Materials Mix And Yield Variances; ACCA Paper F5

Hello. The following question is from my Kaplan Exam Kit: JC Ltd mixes three materials to produce chemical SGR. The following extract from a standard cost card shows the materials to be used in producing 100 kg of chemical SG: Material A: 50 kg @ $10/kg Material B: 40 kg @ $5/kg Material C: 20 kg @ $9/kg Total Kgs: 110 During October 23,180 kg of SGR were produced using the following materials: Material A: 13,200 kg Material B: 7,600 kg Material C: 5,600 kg Total Kgs: 26,400 Required: a) What is the total material yield variance? b) What is the total material mix variance? The way I answered the question is as follows: a) Material Yield Variance = SQSP - AQ(Standard Mix)SP Standard Mix: Material A: 50kg/110kg = 45% Material B: 40kg/110kg = 36% Material C: 20 kg/110kg = 19% SQSP (A) = (23,180 kg x 100/110) x 45% x $10 = $94,827 SQSP (B) = (23,180 kg x 100/110) x 36% x $5 = $37,931 SQSP (C) = (23,180 kg x 100/110) x 19% x $9 = $36,034 Total = $168,792 AQ(SM)SP (A) = 23,180 kg x 45% x $10 = $104,310 AQ(SM)SP (B) = 23,180 kg x 36% x $5 = $41,724 AQ(SM)SP (C) = 23,180 kg x 19% x $9 = $39,638 Total = $185,672 Material Yield Variance = $168,792 - $185,672 = $16,880 Adv. (And voilà! The correct answer must be $7,216 Adv :-) ) b) Material Mix Variance = AQ(SM)SP - AQSP Total AQ(SM)SP (as above) = $185,672 AQSP (A) = 26,400 kg x $10 = $264,000 AQSP (B) = 26,400 kg x $5 = $132,000 AQSP (C) = 26,400 kg x $9 = $237,600 (it just doesn't seem right... The answer is $9,200 Adv) I really, really need help, because I have the feeling that the question is not so difficult, but as you can clearly see, I cannot answer correctly. Thank you!