Suppose that under severe operation conditions, the lifetime, in months, of a transisitor is exponentially distributed with parameter ? = 0.2.
a. Find the probability that such a transistor lasts longer than 8 months.
b. Find the probability that the lifetime of a transistor is between 4 and 10 months.
c. Suppose 10 transistors are operating independently. Find the probability that at least 2 of them last longer than 8 months.
d. Find the probability that more than 8 fail before 10 months.