According to the U.S. Energy Administration, the mean monthly household electric bill in the United States is $99.70 with a standard deviation of $20. Given that household electric bills follow a...

According to the U.S. Energy Administration, the mean monthly household electric bill in the United States is $99.70 with a standard deviation of $20. Given that household electric bills follow a Normal Distribution, what is the probability that a randomly chosen household electric bill:

 a)  is over $131.50?

 b)  is less than $80?

 c)  is between $85.50 and $110.50?

 d) is either higher than $105 or less than $90?