Xavier, Yvonne, and Zelda each try independently to solve a problem. If their individual probabilities for success are 1/5, 1/2 and 5/8, respectively, what is the probability that Xavier and Yvonne, but not Zelda, will solve the problem? Choices:  A) 11 / 8  B) 3 / 80  C) 9 / 64  D) 5 / 64  E) 3 / 64

Rationale: "p ( xavier will solve ) = 1 / 5 p ( yvonne will solve ) = 1 / 2 p ( zelda will not solve ) = 1 - 5 / 8 = 3 / 8 . now , we need to multiply all this ps to find an answer : p = ( 1 / 5 ) * ( 1 / 2 ) * ( 3 / 8 ) = 3 / 80 . ans . b ."
Answer: B