#!/usr/bin/ruby
# ranges_case_when.rb

puts "Student grading system"
print "Enter student mark: "
mark = gets.chop.to_i

grade = case mark
	when 80..100	: 'A'
	when 60..79		: 'B'
	when 40..59		: 'C'
	when 0..39		: 'D'
	else "Unable to determine grade. Try again."
end

puts "Your grade is #{grade}"