Simodong Ltd. uses standard costing for its machine-paced production of printing equipment. Data regarding production during December are as follows: $718,000 Variable manufacturing overhead costs incurred Variable manufacturing overhead cost rate Fixed manufacturing overhead costs incurred Fixed manufacturing overhead costs budgeted $11.0/standard machine-hour $305.000 $280.000 Denominator level in machine-hours 73,000 Standard machine-hour allowed per unit of output Units of output 1.3 65,500 Actual machine-hours used 81.875 Required: a. Prepare an analysis of all manufacturing overhead variances using the 4-variances analysis framework! b. What are the possible causes of the variable manufacturing overhead variances?