Ankara Manufacturing Sdn. Bhd. (AMSB), uses a standard cost system to account for the costs of its one product. Variable overhead standards are 14 hours of labor at a standard rate of RM9. Fixed overhead is applied at a rate of RM150 per unit, based on budget production of 650 units. During July, AMSB produced 600 units. Payroll totaled RM112,930 for 8,770 hours worked. The overhead incurred was RM77, 490 variable and RM98, 750 fixed. (a) Calculate the variable overhead rate variance. (b) Calculate the variable overhead efficiency variance. (c) Calculate the fixed overhead spending variance. (d) Briefly discuss a factor to consider when investigating variance