Required: Williams Incorporated produces fluorescent light bulbs 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 $69,300 and $51,900, respectively, and the associated cost drivers are 7,800 and 4,900 packs, respectively. What is the value for b (the variable cost per unit)? What is the value for a (the fixed quantity)