Refer to the following 2 Questions:

A sample of 10 observations represents a study on driving speed and fuel efficiency (miles). Partial data and calculations are given below. Obs Speed Miles speed-42 miles-27 (speed-42)12 (miles-27)^2 (speed-42)(miles- 27) 30 28 -12 144 -12 2 50 25 8 -2 64 4 -16 . 10 55 25 13 -2 169 4 -26 Total 420 270 0 0 1660 164 -475 Mean 42 27The standard deviation of speed is closest to