An airplane is flying at a speed of 350 mi/h at an altitude of one mile and passes directly over a radar station at time t=0.

Question

a) Express the horizontal distance d (in miles) that the plane has flown as a function of t.

I really don't know... would it be something like d= t . a + b?

b) Express the distance s between the plane and the radar station as a function of d.

c) Use composition to express s as a function of t.

Please Help. Explanations also would be nice, so I can see how to do it.