At an activity level of 9,000 machine-hours in a month, Moffatt Corporation's total variable maintenance cost is $390,240 and its total fixed maintenance cost is $368,280. What would be the total variable maintenance cost at an activity level of 9,300 machine-hours in a month? Assume that this level of activity is within the relevant range. Select one: O a. $390,240 O b. $380,556 O c. $758,520 O d. $403,248