Larker Brothers, Inc., used the high-low method to derive its cost formula for electrical power 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 high level of activity was 3,300 machine hours, then the low level of activity was:

3,000 machine hours

3,200 machine hours

3,100 machine hours

2,900 machine hours