Assume that the best cost driver that Sony had for variable factory overhead in the assembly department is machine hours. During April, the company budgeted 480,000 machine hours and $5,000,000 for its Texas plant's assembly department. The actual vehicle overhead incurred was $5,200,000 which was related to 500,000 machine hours. Show all work please a. determine the variable overhead spending variance b. determine the variable overhead effectiveness variance