Gregory Enterprises has identified three cost pools to allocate overhead costs. The following estimates are provided for the coming year:

Cost Pool	Overhead Costs	Cost driver	Activity level
Supervision of direct labor	$320,000	Direct labor-hours	800,000
Machine maintenance	$120,000	Machine-hours	960,000
Facility rent	$200,000	Square feet of area	100,000
Total overhead costs	$640,000

The accounting records show the Mossman Job consumed the following resources:

Cost driver	Actual level
Direct labor-hours	200
Machine-hours	1,600
Square feet of area	50

If direct labor-hours are considered the only overhead cost driver, what is the single cost driver rate for Gregory Enterprises? a. $0.50 per direct labor-hour b. $0.80 per direct labor-hour c. $0.40 per direct labor-hour d. $1.20 per direct labor-hour