Heidi makes rag quilts. Each child-sized quilt contains 4.25 yards of flannel priced at $4.80 per yard and thread costing $0.24 per quilt. Heidi also allows 0.10 yards of fabric for waste per quilt. Direct labor for each quilt requires 2 hours of cutting and 4 hours of sewing. Cutters direct labor rate is $7.25 per hour, and sewers direct labor rate is $8.50 per hour. Rest periods of 0.01 hours per quilt are allowed for both sewers and cutters, with an additional 0.02 hours per quilt allowed for machine downtime. What is the standard direct materials cost per quilt?

a. $17.80

b. $21.12

c. $19.50

d. $21.95