A test to determine whether a certain antibody is present is

A test to determine whether a certain antibody is present is effective 99.3% effective. The probability of a test coming back positive when the antibody is not present is 0.007%. Suppose the test is given to four randomly selected people who do not have the antibody.

(a) What is the probability the test comes back negative for all four people?

(b) What is the probability the test comes back negative for at least one of the four people?