Four CDs must be bought to receive a gift card from an <em>online</em> store.
<h3>How to determine the least number of CDs to be bought to receive a gift card</h3>
The <em>total</em> costs are equal to the sum of the <em>shipping</em> cost and the total related to the number of <em>acquired</em> CDs (n). The number of gift cards (m) is equal to the total costs divided by <em>minimum spent</em> money, that is, $ 50. We need to solve the following inequation to find the minimum quantity of CDs:
(12 · n + 5)/50 > 1
12 · n + 5 > 50
12 · n > 45
n > 45/12
n > 3.75
Four CDs must be bought to receive a gift card from an <em>online</em> store.