5. Volume of units and the related costs are shown below: Units Sold Salaries Commissions Rent Maintenance Utilities 25 $5,000 $2,500 $2,300 $8,750 $1,000 50 $5,000 $5,000 $2,300 $12,500 $2,000 75 $5,000 $7,500 $2,300 $16,250 $3,000 Based on the above information which of the following costs would be fixed? a. Only Salaries. b Only Rent. c. Salaries, Rent and Maintenance d. Salaries and rent only. c. None of the costs are fixed