please show all steps and calculations:

Jason Manufacturing and Trading Company Limited produces several kitchen products, one of which is a R grinder. One Jack grinder has a prime cost of 4.2, which includes 10 minutes of direct labour (costed at 7.4 per hour). Each unit uses 15 minutes of machine time.

The company's management accountant has estimated the following totals for the coming financial year, 2019:

Machine hours available in the factory	30,000 hours
Direct labour hours available	60,000 hours
Total production overheads	300,000"

Required:

"What is the estimated production cost of one R grinder if:"

1. "production overheads are absorbed on the basis of machine hours?"
2. "production overheads are absorbed on the basis of labour hours?

"The managing director of Jason Manufacturing and Trading Company Limited has very little knowledge about the overhead application. You are required to provide a brief explanation for the following questions:

1. "Why do companies use predetermined overhead rates rather than actual manufacturing overhead costs to apply overhead to jobs?
2. "What is a plantwide overhead rate? Why are multiple overhead rates, rather than a plantwide overhead rate, used in some companies?