Im having trouble understanding mixture problems. (and all the other ones like distance,work rate)

So my question is...

Victor is making orange juice. He has one pitcher that contains 2 quarts of 50% concentrate, and another pitcher that contains 4 quarts of 20% concentrate. If he combines the two pitchers, how many quarts of water must he add so that he ends up with a mixture containing 25%?

A) 0.5

B)1

C) 1.2

D) 2.4