Computers in some vehicles calculate various quantities related to performance. One of these is fuel efficiency, or gas mileage, usually expressed as miles per gallon (mpg). For one vehicle equipped in this way, the miles per gallon were recorded each time the gas tanked was filled, and the computer was then reset. Here are the mpg values for a random sample of 20 of these records: 40.2
44.2
38.3
47.8
44.2
35.5
38.3
45.1
45.6
49.1

47.3
44.3
44.4
37.8
51.4
48.4
49.0
42.4
43.2
45.8

Requried:
a. Find the mean.
b. Find the standard deviation.
c. Find the standard error.