A test to determine whether a certain antibody is present is 99.3​% effective. This means that the test will accurately come back negative if the antibody is not present​ (in the test​subject).
The probability of a test coming back positive when the antibody is not present​ (a false​ positive) is 0.007.
Suppose the test is given to seven randomly selected people who do not have the antibody. ​
(a) What is the probability that the test comes back negative for all seven ​people?