Hi guys, please help with this question:

In a contest, an athlete competes against a robot to see who can climb up a 16m rope faster. The athlete climbs up x m in each of his first 2 pulls; (x - 0.02)m in each of his next 2 pulls; and every subsequent pair of pulls shows a similiar decrease of 2cm from the previous pair.

Show that the distance he travels after 2n pulls is 2nx - 0.02n(n - 1).

I think I am supposed to use the sum of arithmetric progression formula but I am kind of confused with the question...

Thanks in advance!