A certain drug treatment cures 90% of cases of hookworm in children. Suppose that 20 children suffering

Question:

A certain drug treatment cures 90% of cases of hookworm in children. Suppose that 20 children suffering from hookworm are to be treated, and that the children can be regarded as a random sample from the population. Find the probability that
(a) All 20 will be cured.
(b) All but 1 will be cured.
(c) Exactly 18 will be cured.
(d) Exactly 90% will be cured.