Answer:
64
Step-by-step explanation:
Given that an advisor to the mayor of a large city wants to estimate, within 3 minutes, the mean travel time to work for all employees who work within the city limits.
Let X be the random variable denoting the time for employees to travel within city limit
Std dev of X 
For 95% confidence interval Z critical 1.96 is used because population std dev is known
Margin of error 
i.e. 
where n is the desired sample size.
Simplify to get

Hence atleast 64 employees should he poll
Well the greatest number of groups is 35 groups of 1, but some other group sizes are 7 groups of 5 and 5 groups of 7.
The answer will be x=2i,-2i
First you will need a piece of paper, well not really. All this problem is involving is 740
+ 710
=1,500 meters