In the last 6 months, demand for one of Appleby Company's products has dropped off considerably, due mainly to it becoming obsolescent as a result of technological change. Knowing that the equipment used in the manufacture of this product may not be easy to sell, Appleby spent $50,000 on consultants to determine whether it could use the equipment to produce a new product under license by another company. The consultant has determined that this product would have variable production costs of $65 per unit and should sell at a price of $90/ unit. The licensing royalty is 5% of gross product revenue. Estimated annual demand is 20,000 units per year. Additional annual operating costs related to this product are $30,000/ year (excluding depreciation). Depreciation on the equipment is $15,000. Annual depreciation expense is a: a. Sunk cost b. Relevant cost c. Both sunk and Irrelevant cost d. Irrelevant cost