An economy is employing 2 units of capital, 5 units of raw materials, and 8 units of labor to produce its total output of 640 units. Each unit of capital costs $10; each unit of raw materials, $4; and each unit of labor, $3. The per-unit cost of production in this economy is _____.

a. $0.10.
b. $0.50.
c. $1.00.
d. $0.05.