A convenience store sell pre-paid mobile phones. It purchases them for $12 each and uses a mark up rate of 250%. What is the mark-up amount for the phones? What is the retail price of the phones after the mark up?

The convenience store has a markup amount of $30 on the pre-paid mobile phones and the retail price is $42

Step-by-step explanation:

The purchase price of the pre-paid mobile phones is $12.

The convenience store uses a markup rate of 250%.

The markup amount is:

250 * 12 / 100 = 30

The retail price is the purchase price plus the markup amount:

Retail price = $12 + $30 = $42

The convenience store has a markup amount of $30 on the pre-paid mobile phones and the retail price is $42