nightshade industries produces and sells a product that has a variable costs of $$5$ per unit and fixed costs of $$400,000$ per year. if production increases from $50,000$ units to $55,000$ units, the total costs will: a$.$ increase by $$25,000.$ B$.$ decrease by $$0\mathrm{.}78$ per unit. C$.$ decrease by $$4\mathrm{.}55$ per unit. D$.$ stay the same