Tax accountant. A recent study of IRS audits showed that, for estates worth less than $5 million, about 1 out of 7 of all estate tax returns are audited, but that probability increases to 50% for estates worth over $5 million. Suppose a tax accountant has three clients who have recently filed returns for estates worth more than $5 million. What are the probabilities that:

a) All three will be audited?

b) None will be audited?

c) At least one will be audited?

d) What did you assume in calculating these probabilities?