Taran Company incurred the following costs for the months of January and February: Type of Cost January February Insurance $ 5,000 $ 5,000 Utilities 4,000 5,000 Depreciation 3,500 3,500 Materials 10,000 20,000 If output was 5,000 units in January and 10,000 units in February, we can assume that: a.utilities and materials are variable costs. b.utilities, insurance, and depreciation are fixed costs. c.materials are the only variable cost. d.insurance and depreciation are mixed costs.