please help with explanation

Boron Chemical Company produces a synthetic resin that is used in the automotive industry. The company uses a standard cost system. For each gallon of output, the following direct manufacturing costs are anticipated: During December of the current year, Boron produced a total of 2, 600 gallons of output and incurred the following direct manufacturing costs: Boron records price variances for materials at the time of purchase. Prepare journal entries for the following events and transactions: Purchase, on credit, of direct materials. Direct materials issued to production. Direct labor cost of units completed this period. Direct manufacturing cost (direct labor plus direct materials) of units completed and transferred to Finished Goods Inventory. Sale, for $250 per gallon, of 2, 200 gallons of output