A city council collected data on driving speeds in order to decide on appropriate speed limits. On a major street the mean speed was

39.6

mph, with a standard deviation of

4

mph.

On a residential street, speeds had a mean of

23.8

mph and a standard deviation of

2

mph.

Relative to the other traffic on that street, which of the following speeds is greater:

35

mph on the major street or

21

mph on the residential

street?

Show the calculations that justify your answer; round the results to two decimal places.