Since aquamarines are available in large sizes, there is no incremental increase in value per carat for large gems. A 50-carat aquamarine will be worth the same price per carat as a single carat gem of equal quality. The gem price is dependent on clarity, depth of color, and to a lesser extent the purity of color.
The IF function is one of the most popular functions in Excel, and it allows you to make logical comparisons between a value and what you expect. So an IF statement can have two results. The first result is if your comparison is True, the second if your comparison is False.
What we really need is way to make our spreadsheet do this automatically. While you might never have used it before, the IF function can simplify these kinds of problems. The IF function can look at a value in a cell to see if it meets a basic condition (in our example, if the value is greater than or equal to 50).