At an activity level of 6,900 units in a month, Zelinski Corporation's total variable maintenance and repair cost is $408,756 and its total fixed maintenance and repair cost is $230,253. What would be the total maintenance and repair cost, both fixed and variable, at an activity level of 7,100 units in a month? Assume that this level of activity is within the relevant range. $648,270 $639,009 $650,857 $657,531