Light manufacturers produces energy-efficient light bulbs. in one 8-hour shift, they incur the following costs to make 4,000 light bulbs: use 250 lbs. of glass for a total cost of $1,016. use 500 lbs. of coal to keep the fire going to melt and shape glass for a total cost of $1,280. use 8,000 filaments for a total cost of $1,120. use 4,800 feet of wire for a total cost of $156. use 4,000 light bulb bases for a total cost of $1,480. use 128 man-hours for a total cost of $2,500. what are the direct material costs for making one light bulb?
a : $0.943.
b : $0.904.
c : $1.224.
d : $1.263.