The data below relate to Sporty Ltd, a manufacturer of exercise equipment, for August: Standard variable overhead rate Standard quantity of machine hours Budgeted fixed overhead Budgeted output $27 per machine hour 2 hours per unit of output $270 000 15 000 units Actual results for August are as follows: Actual output Actual variable overhead Actual fixed overhead Actual machine time 13 500 units $757 350 $274 500 29 700 machine hours Required: Calculate the following variances, indicating whether each variance is favourable or unfavourable: 1. variable overhead spending variance 2. variable overhead efficiency variance 3. fixed overhead budget variance 4. fixed overhead volume variance