Ivanhoe Corporation manufactures a single product. Monthly production costs incurred in the manufacturing process are shown below for the production of 3,300 units. The utilities and maintenance costs are mixed costs. The foxed portions of these costs are $420 and $280, respectively, 3,300 $10,500 Production in Units Production Costs Direct materials Direct labor Utilities Property taxes 13.230 2,235 1,400 Indirect labor 6,300 2,660 Supervisory salaries Maintenance Depreciation 1.204 3,360 (a) Identify the above costs as variable, fixed, or mixed. Costs Direct materials Direct labor Utilities Property taxes e Indirect labor . Supervisory salaries Maintenance Depreciation