As output increases, total variable cost:

a. increases at a decreasing rate and then at an increasing rate.

b. increases continuously at a decreasing rate.

c. increases more rapidly than does total cost.

d. increases at a constant rate.

Zeta corporation is a manufacturer of sports caps, which require soft fabric. the standards for each cap allow 2.00 yards of soft fabric, at a cost of $2.00 per yard. during the month of january, the company purchased 25,000 yards of soft fabric at $2.10 per yard, to produce 12,000 caps. what is zeta corporation's materials price variance for the month of january?