During May, Chris Company produced 15,000 chainsaw blades. The standard quantity of materials allowed was 2 pounds of steel per blade at a standard cost of $6 per pound. The actual cost was $8 per pound. The actual pounds of steel that Cisco purchased were 27,000 pounds. All materials purchased were used. Calculate materials usage variance. $24,000 U $18,000 U $24,000 F $18,000 F