Writing linear functions word problems

Blue's Berry Farm charges Percy a total of $\mathrm{\$}24.75$‍ for entrance and $2.5$‍ kilograms of strawberries. The entrance fee is $\mathrm{\$}6$‍, and the price for each kilogram of strawberries is constant.

The total cost $C$‍ for picking strawberries is a function of $x$‍, the kilograms of strawberries picked.

$C=$‍