The monthly utility bills in a city are normally​ distributed, with a mean of $100 and a standard deviation of ​$13. Find the probability that a randomly selected utility bill is​ (a) less...

The monthly utility bills in a city are normally​ distributed, with a mean of $100 and a standard deviation of ​$13.

Find the probability that a randomly selected utility bill is​ (a) less than ​$68​, ​(b) between $87 and ​$100​, and​ (c) more than ​$110.