Fare Calculator App

Fare calculator,

I’m working on creating a booking fare calculator.
There are 28 bus stations,
Base Price is 100 up to 5 bus stations.
Later 50 extra for every 5 bus stations.
Round trip from 1 to 28 is 300 .

Here is my solution,

BASE = 100
stops = (start - end).abs

case stops
when 1..5
  BASE
when 5..10
  BASE + 5
when 10..15
  BASE + 10
when 15..16
  BASE + 15
when (station_array.length - 1)..station_array.length
  200
end