16. Backyard Creations purchased 7,800 feet of copper tubing at a price of $2.30 per foot and used 7,500 feet during the period. The standard quantity allowed for the units produced is 1300 and the standard price of the copper tubing is $2.50 per foot. What is Backyard Creations' direct materials quantity variance for the period? a $460 unfavorable b. $500 unfavorable c. $?'50 unfavorable d $1,250 unfavorable