1. At periodic intervals, the Acme Bank has its lighting and ventilation system thoroughly overhauled. Since this process causes some disruption in bank operations, the bank's managers want the overhaul to proceed in an orderly and efficient manner. To facilitate the project planning, the Acme managers have broken the project into specific tasks. These tasks, along with their immediate predecessors and estimated duration times for fast and slow workers, respectively, are indicated in the following table.

Task FastTime SlowTime Predecessor (Days) (Days)

A. Check electrical panels and circuits - 1.5 3 B. Replace all light bulbs - 4 7 C. Clean and service compressor in air conditioner A 2 4 D.Test and service heater A 3 5 E. Refill oil tanks - 0.5 5 F. Clean and service electro-static filter C, D 1 3 G. Clean and service blower unit C. D 2 4 For each task, Acme managers can hire one of two possible contractors to perform the task. For each task, a less expensive contractor can be hired who charges

$20 per day but works at the slow rate, or a more expensive contractor can be hired at $50 per day who works at the fast rate. Because tasks A and B both require the services of an electrical contractor, Acme managers have required that the same contractor perform both tasks A and B. Also, the cost of filling the oil tanks is not a function of the time required; the cost is strictly a function of the number of gallons of oil needed (estimated currently at 15,000 gallons @ $1.75/gallon). Acme Bank has hired you to manage this project; they have stated that they want the project completed at the lowest possible cost, but that the project must be completed within nine days in order to minimize disruption. Determine which contractors should be hired; what is the estimated total cost for the overhaul? When should each contractor begin work?