Miramar Tire and Rubber Company has capacity to produce 250,000 tires

Miramar Tire and Rubber Company has capacity to produce 250,000 tires. Miramar presently produces and sells 200,000 tires for the North American market at a price of $40 per tire. Miramar is evaluating a special order from a South American automobile company, Rio Motors. Rio Motors is offering to buy 40,000 tires for $20 per tire. Miramar’s accounting system indicates that the total cost per tire is as follows:

Miramar pays a selling commission equal to 4% of the selling price on North American orders, which is included in the variable portion of the selling and administrative expenses. However, this special order would not have a sales commission. If the order was accepted, the tires would be shipped overseas for an additional shipping cost of $1.50 per tire. In addition, Rio has made the order conditional on Miramar Tire Company receiving a Brazilian safety certification. Rio estimates that this certification would cost Miramar Tire $20,000.

When required, round all per unit answers to nearest cent. Enter all amounts as positive numbers.
Direct Materials 10.00
Direct Labor 5.00
fact overhead(45% variable) 4.00
Selling and Admin expens (75% var) 3.00
Total 22.00

I just need to know how the 18.95 for the variable special product cost was received.

Proposal to Sell to Rio Motors
August 7, 2012
Per Unit
Total
Differential revenue from accepting special offer

Total differential costs

$

$

$

Differential costs from accepting special offer:

Direct materials

$

Direct labor

$

$

Total differential costs

$