Can someone help and explain how to answer this step by step so that I know how to do it? I don't know if I did the first part right. The figure shows the depths of a submarine.

a. Find the vertical distance traveled by the submarine. Write your answer as a decimal.
The vertical distance is -410.7 feet.
Work: -725.6 - -314.9 = -410.7 (-410.7 is negative because both decimals are the same signs)
b. Find the mean hourly vertical distance traveled by the submarine. Write your answer as a decimal.
The mean hourly distance is _ feet per hour.