Help, am confused with this question:

Jack and Dan have a race on an escalator which is moving downwards. Dan takes 2 steps per second as he moves down the escalator and he reaches the bottom after taking 80 steps.

a) find the time he takes to reach the bottom

b) the escalator moves downwards at one and a half steps per second. Find the number of escalator steps visible at one moment.

c) Dan turns round immediately he reaches the bottom and runs back up the same escalator at U steps per second. It takes him 200 steps to reach the top. Find the time Dan takes on the upward journey and his speed, U, in steps/second.

d)Jack descends the same escalator at 2 1/2 steps per second. He too, immediately turns round and runs back up. Find, correct to one decimal place, the number of steps per second at which Jack must run up the escalator to take the same overall time as Dan?