Gribble Company's high and low level of activity last year was 60, 000 units of product produced in May and 20, 000 units produced in November. Machine maintenance costs were $156, 000 in May and $60, 000 in November. Using the high-low method, determine an estimate of total maintenance cost for a month in which production is expected to be 45, 000 units. $120, 000 $117, 000 $135, 000 $144, 000