I need help on these hw questions please

A) Consider events A and B.If P(A) = 0.35, P(B) = 0.5 and P(A/B) = 0.60, then the probability of at least one of these events to occur is:

B ) A firm buys 70% of its microcomputer supplies from vendor A and the remainder from vendor B.Of these orders, 10% of those from vendor A and 20% from vendor B are delivered later than promised.A late shipment of supplies has just arrived.What is the probability that it came from vendor B?

C ) Suppose that on any given day the owner of a yard service business will earn $25 on a single job if it does not rain, but will earn nothing if it rains.Further suppose that the probability of rain on any given day is 0.2.What is the expected gain for the owner for this job?