Please show your work... How do you do this?

Question

I do not get how the answer is c(m)=0.9+0.6(5m-1) especially where 5m-1 comes from...please explain.

A taxicab charges $.90 for the first 1/5 mile and $.60 for each additional 1/5 mile. If a customer rides in this cab for m miles (m>1/5) , which of the following functions descibes the cost,c(m), of this tax ride in dollars?

Answer 1

There are five parts in the mile, and if the customer is riding more than 1/5 of a mile, then the first 1/5 of the mile is separate. All five parts cannot be included in the calculation since the .9 is separate.