Customers depart from a bookstore according to a Bernoulli process with parameter p = 0.15 (per minute). Each customer buys a book with probability 2/3, independent of everything else.

1. Find the distribution of the time until the first sale of a book.

2. Find the probability that no books are sold between 1:004:00 pm on some particular day.

3. Find the expected number of customers who buy a book between 1:004:00 pm on some particular day.