Required: Use any of the methods explained in the chapter to compute the following variances. (Indicate the effect of each variance by selecting "Favorable" or "Unfavorable". Select "None" and enter "O" for no effect (i.e., zero variance).) a. Variable-overhead spending variance b. Variable-overhead efficiency variance c. Fixed-overhead budget variance d. Fixed-overhead volume variance Required: Use any of the methods explained in the chapter to compute the following variances. (Indicate the effect of each variance by selecting "Favorable" or "Unfavorable". Select "None" and enter "O" for no effect (i.e., zero variance).) a. Variable-overhead spending variance b. Variable-overhead efficiency variance c. Fixed-overhead budget variance d. Fixed-overhead volume variance