Which of the following is MOST LIKELY described as a mixed cost? A$.$ Joe's Fish Farm purchases fish food at a cost of $$100$ per barrel plus $$10$ shipping B$.$ The cost of a phone line to your home which is billed at $$30$ per month plus $7$tax C$.$ Millicent's Fine Hats pays its workers $$10$ per hour and $$1$ per hat produced. D$.$ During the summer, Steve's Squash Farm buys fertilizer costing $$0\mathrm{.}50$ per plant for its $100$ plants. During the winter, Steve pays $$0\mathrm{.}50$ for the fertilizer for its $50$ plants