An Investment Advisor Recommends the Purchase of Shares in Probaballisitics,Inc

Essay

An investment advisor recommends the purchase of shares in Probaballisitics,Inc.He has made the following predictions:
P(Stock goes up 20% | Rise in GDP)= .6
P(Stock goes up 20% | Level GDP)= .5
P(Stock goes up 20% | Fall in GDP)= .4
An economist has predicted that the probability of a rise in the GDP is 30%,whereas the probability of a fall in the GDP is 40%.
a.What is the probability that the stock will go up 20%?
b.We have been informed that the stock has gone up 20%.What is the probability of a rise or fall in the GDP?