Slip Heel Ltd manufactures two types of shoes in its factory. A typical monthly budget is as follows: Shoe Type I Monthly output 5,040 units Time per unit 24 minutes Shoe Type II 10,560 units 36 minutes Unavoidable non-productive time is 25% of productive time and is paid 9 per hour. Operatives are paid 8 per unit of shoe type I produced and 14 per unit of shoe type II. What would be the monthly cost of operatives' wages in the factory?