Josh Has Been Given Two Assignments, Assignment a and Assignment

Multiple Choice

Josh has been given two assignments, assignment A and assignment B.He estimates that the chance of getting a passing grade on assignment A is 60% and the chance of getting a passing grade on assignment B is 50%.If Josh gets a passing grade on assignment A, he figures his chances of getting a passing grade on assignment B increase to 70%.How likely is it that Josh gets a passing grade on assignment A but not on assignment B?

A) .30
B) .42
C) .18
D) .49
E) .85