Keef Corporation uses the high-low method to derive its cost formula for electrical power cost, which is a mixed cost. According to the cost formula, the variable cost per unit of activity is $4 per machine-hour. Total electrical power cost at the high level of activity was $19,200 and at the low level of activity was $18,400. If the low level of activity was 3,100 machine hours, then what was the high level of activity? 3,200 machine hours 3,275 machine hours 3.300 machine hours 3,375 machine hours None of the above