Have you ever tried to get out of jury duty? About 25% of those called will find

Question:

Have you ever tried to get out of jury duty? About 25% of those called will find an excuse (work, poor health, travel out of town, etc.) to avoid jury duty. If 12 people are called for jury duty:
(a) what is the probability that all 12 will be available to serve on the jury?
(b) what is the probability that 6 or more will not be available to serve on the jury?
(c) Find the expected number of those available to serve on the jury. What is the standard deviation?