nenshu.rb

#!/usr/bin/env ruby

HOUR = 1

def jikyu(work_time_per_month: , nenshu: )
  gekkyu = nenshu / 12.0
  gekkyu / work_time_per_month
end

[
  { work_time_per_month: HOUR * 8 * 5 * 4, nenshu: 3_000_000 },
  { work_time_per_month: HOUR * 8 * 5 * 4, nenshu: 8_000_000 },
  { work_time_per_month: 80, nenshu: 8_000_000 },
].each do |data|
  puts work_time: data[:work_time_per_month], jikyu: jikyu(work_time_per_month: data[:work_time_per_month], nenshu: data[:nenshu]), nenshu: data[:nenshu]
end