Each of A, B, C and D is a positive integer with the proviso that A ≤ B ≤ C ≤ D ≤ 20.
Determine the total number of quadruplets (A, B, C, D) such that A*B*C*D is divisible by 50.
(In reply to Solution
I am not sure where the disagreement lies, but I think it may be in your statement "at least 2 must be from set p" if perhaps that is being interpreted as "two different values from set p". This would exclude e.g. (6 9 10 10) = 1500, and many more where the same member of p occurs twice (or even three or four times), but the other integers are not in p. Perhaps we have different readings of the puzzle text.