Walsh Corporation's relevant range of activity is 2,000 to 6,000 units. When it produces and sells 4,000 units, its average costs per unit are as follows: Direct materials Direct labor Variable manufacturing overhead Fixed manufacturing overhead Fixed selling expense Fixed administrative expense Sales commissions $6.75 $3.86 $2.76 $2.46 $1.06 $0.37 $2.17 If 5,000 are produced, the total amount of direct manufacturing costs incurred is closest to: a. $53,050 b. $66,850 c. $70,650 d. $65,350