A. To find the expected pay per mile if the cab travels 6 miles:
From the figure, we observe that,
The expected pay or the average cost per mile if the cab travels 6 miles is 3.
B. To find the value that will the average cost per mile never go below:
From the figure, we observe that,
The value that will the average cost per mile never go below zero.
Because the cost should not be negative. Also, distance in miles can not be negative.