Answer:
If the wholesale price of the king-size mattress is $359.00, and the specialty store marks up the price by 40%, the price Debra would pay at the specialty store is:
Wholesale price + Mark-up amount = Price at specialty store
$359.00 + 40% of $359.00 = $359.00 + $143.60 = $502.60
Therefore, Debra would pay $502.60 for the mattress at the specialty store.