Sales Mix Variance; Kaplan Exam Kit

Hello, Mr Moffat. Jones' monthly absorption costing variance analysis report includes a sales mix variance, which indicates the effect on profit of actual sales mix differing from the budgeted sales mix. The following data are available: PRODUCT X Selling price = $12 (Variable Cost) = ($6) (Fixed Cost) = ($2) Standard net profit per unit = $4 PRODUCT Y Selling price = $11 (Variable Cost) = ($2) (Fixed Cost) = ($3) Standard net profit per unit = $6 July sales (units): PRODUCT X Budget = 3,000 Actual = 2,000 PRODUCT Y Budget = 6,000 Actual = 8,000 What is the favourable sales mix variance for July? A) $8,000 B) $5,333 C) $4,000 D) $2,667 My answer (which is wrong) is C) $4,000. Actual mix = 2,000 units + 8,000 units = 10,000 units Standard Mix = (10,000u x 4/10) + (10,000u x 6/10) = 4,000u + 6,000u Standard Profit from Actual Mix = (2,000 units x $4) + (8,000 units x $6) = $56,000 Standard Profit from Standard Mix = (4,000 units x $4) + (6,000 units x $6) = $52,000 Difference = $4,000 The correct answer is D) $2,667 10x - (2 x $4 + 8 x $6) = $2,667 I will be really grateful, if you explain to me why is answer D correct, because I... I just don't get it. I cannot even understand their solution. Thank you.