Swifty Co. produces wooden boxes. The companys standards per box require 7 boards, each costing $9 per board, and half of an hour of direct labour. The standard labour rate is $15 per hour. In August, Swifty Co. purchased 11920 boards for a total cost of $123600. It used 11600 boards to manufacture 1960 boxes. Total labour hours were 1080 hours, and total labour costs were $16350. What was the materials purchase price variance for August? $16320 F $16320 U $19200 F $19200 U