Answer: C. 56%
Explanation:
Given : The cost of MP3 player = $64.25
The selling price of MP3 player = $99.99
We know that the mark up price =

thus, the mark up price=

Now the percent of mark up =

⇒ The percent of mark up =

⇒ The percent of mark up =

Hence, the mark up percent = 56 %