stardard costing

1) Variable cost 8 Fixed cost 2 10 Standard profit 5 Standard selling price 15 The sales volume variance reported for last period was $9,000 adverse. AD Ltd is considering using standard marginal costing as the basis for variance reporting in future. What would be the correct sales volume variance to be shown in a marginal costing operating statement for the last period? the answer is $12600 F How did they come up with Favourable variance? 2) The budgeted contribution for HMF Co for June was $290,000. The following variances occurred during the month. Fixed overhead expenditure variance 6,475 Favourable Total direct labour variance 11,323 Favourable Total variable overhead variance 21,665 Adverse Selling price variance 21,875 Favourable Fixed overhead volume variance 12,500 Adverse Sales volume variance 36,250 Adverse Total direct materials variance 6,335 Adverse. my question is, why wasn't the fixed overhead variance not included in the calculation?