Alison Reece manages the Beach Candy Shop, which was expected to sell 4,000 servings of its trademark candy during July. Each serving was expected to contain 6 ounces of candy. The standard cost of the candy was $0.50 per ounce. The shop actually sold 3,800 servings and actually used 22,100 ounces of candy.

Required
a. Compute the materials usage variance.
b. Explain what could have caused the variance that you computed in Requirement a.