Tom parks his car at a meter without paying for 1 hour. A parking enforcement officer checks for parking violations an average of 3 times per hour. However, the officer's eyesight is poor and sometimes reads the meter incorrectly. Because of this, he writes a ticket for a violation only 80% of the time.

(a) What is the probability that the officer checks Tom's meter 4 times?

(b) What is the probability that the officer checks Tom's meter 4 times and gives him a ticket on the 4th time? (The officer did not give a ticket the first 3 times.)