Sirak Yoel, a small service firm, uses the high-low method to estimate electricity cost, which varies in relation to machine hours as follows:

Month	Machine hours	Energy expense
January	220	$1,750
February	190	$1,600
March	170	$1,500
April	200	$1,700

Required:

1. Using the high-low method identify the month that represents:

(a) the highest point and

(b) the lowest point

2. Calculate the following:

(a) The variable cost rate per machine hour of electricity

(b) The total fixed cost per month

3. Write the cost formula for Sirak Yoel. Using the cost formula, calculate the total electricity cost assuming the plant plans to use 250 machine hours in June.