I have a cost accounting question.

The Central Valley Company is a manufacturing firm that produces and sells a single product. The companys revenues and expenses for the last four months are given below.

Central Valley Company
Comparative Monthly Income Statements
	March			April			May			June
Sales in units		5,700			5,200			5,950			6,400
Sales revenue	$	763,800		$	696,800		$	797,300		$	857,600
Less: Cost of goods sold		395,200			368,200			403,700			433,000
Gross margin		368,600			328,600			393,600			424,600
Less: Operating expenses
Shipping expense		68,700			63,700			71,950			74,500
Advertising expense		77,000			77,000			77,000			77,000
Salaries & commissions		176,000			158,700			176,950			187,500
Insurance expense		9,700			9,700			9,700			9,700
Depreciation expense		46,000			46,000			46,000			46,000
Total operating expenses		377,400			355,100			381,600			394,700
Net income	$	(8,800	)	$	(26,500	)	$	12,000		$	29,900

Required:

1.	Management is concerned about the losses experienced during the spring and would like to know more about the cost behaviour. Develop a cost equation for each of the costs.

COGS Y= + $ X

Shipping Y= + $ X

Salaries & Commissions Y= + $ X