1. If month have 31 days and new hire date 12 was calculated = Salary / 30 days(Fixed) * actual working days ( 31-12+1=20)
2. If month have 28 days and new hire date 12 was calculated = Salary / 30 days(Fixed) * actual working days ( 28-12+1=17)
3. If month have 30 days and new hire date 12 was calculated = Salary / 30 days(Fixed) * actual working days ( 30-12+1=19)