Hi guys, as the title stated, I really need some help with a problem (It appeared in my country's OI years ago). I remember it being a problem on Codeforces, the statement goes something like this:

Given N knowledges, numbered from 1 to N, each knowledge i has a cost of S[i] for you to be proficient in it. There are M tests, for each test from 1 to M, it gives you A[i] money, but it has a set of knowledges that require you to be proficient in all of it. Calculate the maximum benefit, if you learn knowledges optimally. For example, ~~~~~
~~~~~ N = 5 ~~~~~
~~~~~

1 2 2 1 3 ~~~~~
~~~~~ M = 4 ~~~~~
~~~~~ A[1] = 2, knowledge requirements of 1 : (1,2) ~~~~~
~~~~~ A[2] = 5, knowledge requirements of 2 : (2,3) ~~~~~
~~~~~ A[3] = 1, knowledge requirements of 3 : (5) ~~~~~
~~~~~ A[4] = 1, knowledge requirements of 4 : (1) ~~~~~
~~~~~ The maximum benefit will be 3, since you learn knowledges (1,2,3) costs 1+2+2 = 5, and the tests 1,2,4 will give you 2+5+1 = 8 profit — cost = 8 — 5 = 3 ~~~~~
~~~~~ Thanks for any help in advance!!!