A novice investor invests in stocks without being fully informed about all the intricacies of the stock market. The probability that his first investment in one market sector is a good stock is 1/3 and that his second investment in an unrelated market sector is a good stock is 1/4. Find the probability that:

a) At least one investment would be a good stock.

b) Both the investments would be good stocks.

c) Only one investment would be a good stock.

d) None of the investments would be a good stock.