Write a function that will charge driving students based on the amount of time they spent in their lessons. This particular school charges for lessons as follows:

Time                            Cost
************************************
Up to 1st hour                   $30
Every subsequent half hour**     $10
** Subsequent charges are calculated by rounding up to nearest half hour.

For example, if student X has a lesson for 1hr 20 minutes, he will be charged $40 (30+10) for 1 hr 30 mins and if he has a lesson for 10 minutes, he will be charged $30 for the full hour.

Out of the kindness of its heart, the driving school also provides a 5 minutes grace period. So, if student X were to have a lesson for 65 minutes, he will only have to pay for an hour. Lessons under 5 minutes are just talks, so they should be considered free.

For a given lesson time in minutes (min), write a function price to calculate how much the lesson costs.

Tests

cost(84)
cost(102)
cost(273)

Good luck!

This challenge comes from kkavita92 on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

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