3. The Lakeshore Hotel's guest days of occupancy and custodial supplies expense over the last seven months were Month March Guest-Days of Occupancy 4,000 Custodial Supplies Exp. $7,500 April May June July August September 6,500 8,000 10,500 12,000 9,000 7,500 $8,250 $10,500 $12,000 $13,500 $10,750 $9,750 Instructions: Using the high-low method, estimate a cost formula for custodial supplies expense. a. b. Using the cost formula you derived above, what amount of custodial supplies expense would you expect to be incurred at an occupancy level of 11,000 guest days