following is a cost data for the equipment maintenance department. this department charges other departments for the actual cost of materials and labor when making equipment repairs. the mangers now want to develop a cost function that explains there overhead costs as a function of the number of service calls made each month.

feb march april may

salary-manager	3000	3000	3000	3200
supplies	470	578	735	650
insurance	200	200	250	250
electricity	59	61	65	62
property taxes			600
repair manuals	90	100	80	90
total	3819	3939	4730	4252
service calls	90	110	140	125

***salaries of all deparment heads are increased annually in may

***insurance rates increse in april

***property taxes are paid in two equal installments in april and october

A. Estimate the departments cost function using analysis in the account level

B. using the cost function estimated in part (A) estimate the overhead cost for June if 135 service calls are expected

C. Calculate the average overhead costs per unit for the four month period. given this average cost what is the estimated total cost for june

D. which estimation method is better - part B or C? why?