Bison Burt’s uses two different grade scales of labour. In the last production period they used 2,500 hours of GS4 and 1,500 hours of GS5. The standard pay rates are $11 per GS4 hour and $15 per GS5 hour. At Bison Burt’s the standard is to use 2 hours of labour per unit produced; 60% GS4 and 40% GS5. During this production period 2,100 units were produced. What are the mix and yield variances for GS4?

a. $1,100 U; $1,320 F

b. $1,500 F; $1,200 F

c. $1,100 F; $1,320 U

d. $400 F; $2,520 F

e. $1,100 U; $1,500 F