Internet services costs $\$0.50$ per minute for the first $8$ minutes and $\$0.20$ a minute there after. What is the best equation which represents the cost of internet in dollars, when time is greater than $8$ minutes.

Question

$\begin{array}{1 1} a)\;8+0.20(x-8) \\ b)\;4+0.20(x) \\ c)\;4+0.20(x+8) \\ d)\;4+0.20(x-8)\end{array}$