Please help explain how to find the following:

Assume the following information:

Direct Materials

$40

per unit

Direct Labor

$20

per unit

Total Estimated Manufacturing Overhead

$8,400,000

Manufacturing overhead is allocated based on estimated direct-labor hours.

Each unit of product requires 1 direct labor hour.

1.Calculate the cost of one unit of product, assuming that the overhead per unit is based on Terri Ronson's estimate of 440,000 hours. (Round all dollar figures to two decimal places.)

a.If 441,000 units were produced, how much overhead was applied to work in process.

2.Calculate the cost of one unit of product, assuming that the overhead per unit is based on her supervisors preferred estimate of 420,000 hours. (Round all dollar figures to two decimal places.)

a.If 441,000 units were produced, how much overhead was applied to work in process.

I am not sure how to find how much overhead was applies