A hotel pays the phone company $$300$ per month plus $$0\mathrm{.}25$ for each call made. During January $7,000$ calls were made. In February $4,000$ calls were made.

Part $1.$ Calculate the hotel's phone bill for January and February.

Part $2.$ Seperate the January phone bill into its fixed and variable components. What is the total?

Part $3.$ What is the marginal cost of one additional phone call in January? $($Round your answer to two decimal places$)$

Part $4$: What was the average cost of a phone call in January? $($Round your answer to $3$ decimal places$)$