Williams Inc. produces fluorescent lightbulbs for commercial use. The accounting manager is attempting to estimate the total cost for the next quarter using the high-low method. He has compiled data and found the high and low costs are $57,400 and $36,900, respectively, and the associated cost drivers are 7,300 and 3,200 packs, respectively. What is the value forb(the variable cost per unit)? What is the value fora(the fixed quantity)?