in the month of May, Williams Company produced 5678 units of a product. The standard cost card indicates the following materials standard per unit of output: 1 kilogram @ $0.5 = $0.50. During May, 16550 kilograms of material were purchased at a total cost of $9213 and 6692 kilograms of materials were used. What is the material price variance for May? Note that a negative number indicates an unfavourable variance. Select one: O a. $507 O b. $938 O c. $-507 O d. $-938