Olivera Corporation's flexible budget performance report for last month shows that actual indirect materials cost, a variable cost, was $45,241 and that the spending variance for indirect materials cost was $2,320 unfavorable. During that month, the company worked 17,100 machine-hours. Budgeted activity for the month had been 17,480 machine-hours. The cost formula per machine-hour for indirect materials cost must have been closest to:

a. $2.82

b. $2.89

c. $2.46

d. $2.51