Runaround Corporation sells running shoes and during January they ran production machines for 21,000 hours total and incurred $15,000 in maintenance costs. During July they ran production machines for 10,000 hours total and incurred $8,400 in maintenance costs. Based on this data, what are the fixed costs? (Round intermediary calculations to the nearest cent.) O A. $8,400 B. $15,000 O c. $42,000 OD. $2,400