Angora Creations Co. manufactures wool sweaters. Costs incurred in making 45,000 sweaters in September included $180,000 of fixed manufacturing overhead. The total absorption cost per sweater was $34.80.

Required:
a. Calculate the variable cost per sweater.
b. The ending inventory of sweaters was 6,400 units lower at the end of the month than at the beginning of the month. By how much and in what direction (higher or lower) would cost of goods sold for the month of September be different under variable costing than under absorption costing?
c. Express the sweater cost in a cost formula.