Answer:
The rate of descent is 4 ft/min.
He will descent 24 ft in 6 min.
Explanation:
Consider the provided information.
He starts at sea level and then descends 10 feet in 2 1/2 minutes.
First convert the mixed fraction as shown:

Therefore the rate of descent is:
The rate of descent =

Hence, the rate of descent is 4 ft/min
Now find In 6 minutes, how much he will descent:

Hence, he will descent 24 ft in 6 min.