On a strand of lights, the expected number of lights that fail to work correctly is 20.

Question:

On a strand of lights, the expected number of lights that fail to work correctly is 20.
a. What is an upper bound on the probability that 30 or more lights fail to work?
b. If the standard deviation is 5, what is a bound on the probability that between 12 and 28 lights fail to work correctly?