can you help me solve this problem please?

A test to determine whether a certain antibody is present is 99.9% effective. This means that the test will accurately come back negative if the antibody is not present (in the test subject) 99.9% of the time. The probability of a test coming back positive when the antibody is not present (a false positive) is 0.001. Suppose the test is given to four randomly selected people who do not have the antibody. (a) What is the probability that the test comes back negative for all four people? (b) What is the probability that the test comes back positive for at least one of the four people? (a) P(all 4 tests are negative ) = (Round to four decimal places as needed.)