This is not a very clear argument though, could anyone rovide something more concise/elegant?
A .... r/2 is integer.
pr/10 = p/5 * r/2
... we cant say whether p/5 is an integer..Insufficient
B .... p is prime
p could be 2,3,4 or 5 or any other prime number. Insufficient
Combine... we still have no conclusion.
Is that elegant enough for you?