#include <bits/stdc++.h>

using namespace std;

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	int t;
	cin >> t;
	for (int i = 0; i < t; ++i) {
		int a, b, k;
		cin >> a >> b >> k;
		cout << (a - b) * 1ll * (k / 2) + a * (k & 1) << endl;
	}
	
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	
	int ans = 0;
	for (int i = 1; i < n - 1; ++i) {
		if (a[i] == 0 && a[i - 1] == 1 && a[i + 1] == 1) {
			++ans;
			a[i + 1] = 0;
		}
	}
	cout << ans << endl;
	
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

const int MAX = 1e6;

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	int n;
	cin >> n;
	vector<int> a(n);
	vector<int> cnt(MAX + 1);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
		++cnt[a[i]];
	}
	long long sum = accumulate(a.begin(), a.end(), 0ll);
	
	vector<int> ans;
	for (int i = 0; i < n; ++i) {
		sum -= a[i];
		--cnt[a[i]];
		if (sum % 2 == 0 && sum / 2 <= MAX && cnt[sum / 2] > 0) {
			ans.push_back(i);
		}
		sum += a[i];
		++cnt[a[i]];
	}
	
	cout << ans.size() << endl;
	for (auto it : ans) cout << it + 1 << " ";
	cout << endl;
	
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

const int MAX = 200 * 1000 + 1;

int n, k;
vector<int> s, t;
vector<int> cnts(MAX);

bool can(int cnt) {
	t.clear();
	for (int i = 0; i < MAX; ++i) {
		int need = min(cnts[i] / cnt, k - int(t.size()));
		for (int j = 0; j < need; ++j) {
			t.push_back(i);
		}
	}
	return int(t.size()) == k;
}

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	cin >> n >> k;
	s = vector<int>(n);
	for (int i = 0; i < n; ++i) {
		cin >> s[i];
	}
	for (auto c : s) {
		++cnts[c];
	}
	
	int l = 0, r = n;
	while (r - l > 1) {
		int mid = (l + r) >> 1;
		if (can(mid)) {
			l = mid;
		} else {
			r = mid;
		}
	}
	if (!can(r)) can(l);
	for (auto it : t) cout << it << " ";
	cout << endl;
	
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	int n;
	cin >> n;
	map<int, int> cnt;
	for (int i = 0; i < n; ++i) {
		int x;
		cin >> x;
		++cnt[x];
	}
	
	vector<int> cnts;
	for (auto it : cnt) {
		cnts.push_back(it.second);
	}
	sort(cnts.begin(), cnts.end());
	
	int ans = 0;
	for (int i = 1; i <= cnts.back(); ++i) {
		int pos = int(cnts.size()) - 1;
		int cur = i;
		int res = cur;
		while (cur % 2 == 0 && pos > 0) {
			cur /= 2;
			--pos;
			if (cnts[pos] < cur) break;
			res += cur;
		}
		ans = max(ans, res);
	}
	cout << ans << endl;
	
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

const long long INF64 = 1e18;

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	int n, k, x;
	cin >> n >> k >> x;
	vector<int> a(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	vector<vector<long long>> dp(n + 1, vector<long long>(x + 1, -INF64));
	
	dp[0][x] = 0;
	for (int i = 1; i <= n; ++i) {
		for (int j = 0; j < x; ++j) {
			for (int p = 1; p <= k; ++p) {
				if (i - p < 0) break;
				if (dp[i - p][j + 1] == -INF64) {
					continue;
				}
				dp[i][j] = max(dp[i][j], dp[i - p][j + 1] + a[i - 1]);
			}
		}
	}
	
	long long ans = -INF64;
	for (int i = n - k + 1; i <= n; ++i) {
		ans = max(ans, *max_element(dp[i].begin(), dp[i].end()));
	}
	if (ans == -INF64) ans = -1;
	cout << ans << endl;
	
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

#define x first
#define y second
#define mp make_pair

typedef long long li;
typedef pair<li, li> pll;

const li INF64 = 1e18;

struct myQueue {
	stack<pll> s1, s2;
	
	int size() {
		return s1.size() + s2.size();
	}
	
	bool isEmpty() {
		return size() == 0;
	}
	
	long long getMax() {
		if (isEmpty()) {
			return -INF64;
		}
		if (!s1.empty() && !s2.empty()) {
			return max(s1.top().y, s2.top().y);
		}
		if (!s1.empty()) {
			return s1.top().y;
		}
		return s2.top().y;
	}
	
	void push(long long val) {
		if (s2.empty()) {
			s2.push(mp(val, val));
		} else {
			s2.push(mp(val, max(val, s2.top().y)));
		}
	}
	
	void pop() {
		if (s1.empty()) {
			while (!s2.empty()) {
				if (s1.empty()) {
					s1.push(mp(s2.top().x, s2.top().x));
				} else {
					s1.push(mp(s2.top().x, max(s2.top().x, s1.top().y)));	
				}
				s2.pop();
			}
		}
		assert(!s1.empty());
		s1.pop();
	}
};

int n, k, x;
vector<int> a;

vector<myQueue> q;
vector<queue<int>> pos;
vector<vector<long long>> dp;

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
#endif
	
	cin >> n >> k >> x;
	a = vector<int>(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}
	q = vector<myQueue>(x + 1);
	pos = vector<queue<int>>(x + 1);
	dp = vector<vector<long long>>(n + 1, vector<long long>(x + 1, -INF64));
	
	dp[0][x] = 0;
	pos[x].push(-1);
	q[x].push(0ll);
	
	for (int i = 1; i <= n; ++i) {
		for (int j = 0; j <= x; ++j) {
			while (!pos[j].empty() && pos[j].front() < i - k - 1) {
				q[j].pop();
				pos[j].pop();
			}
		}
		for (int j = 0; j < x; ++j) {
			if (!q[j + 1].isEmpty()) {
				dp[i][j] = max(dp[i][j], q[j + 1].getMax() + a[i - 1]);
				q[j].push(dp[i][j]);
				pos[j].push(i - 1);
			}
		}
	}
	
	long long ans = -INF64;
	for (int i = n - k + 1; i <= n; ++i) {
		ans = max(ans, *max_element(dp[i].begin(), dp[i].end()));
	}
	if (ans == -INF64) ans = -1;
	cout << ans << endl;
	
	return 0;
}