A niche share rating agency has three rating categories: Low, Medium and High. In the last 4 years, 50% of the shares were rated Low, 30% were rated Medium, and 20% were rated High. Of the shares rated Low, 60% were issued by CitiBank, 10% were issued by St. George, and 30% by Rabobank. Of the shares rated Medium, 50% were issued by CitiBank, 20% by St George, and 30% by Rabobank. Of the shares rated high, 90% were issued by Citibank, 5% by St. George, and 5% by Rabobank. Calculate:

a) If a new share is to be issued by CitiBank, what is the probability that it will receive a low rating?

b) What proportion of the shares are issued by CitiBank?

c) What proportion of the shares are issued by St.George?