A solution to last week's challenge can be found here. 
If you're familiar with the Formula tool in Designer, you know that there aren't many things you can't do with it. But just because you can do something doesn't mean that you should. There are some tasks that can get a little repetitive when you have to do them over and over again. In those instances it can be more efficient to think about ways to make the process a little more dynamic. This also serves you well as you begin automating processes because it can keep workflows from breaking when datasets change.
For this week's challenge, we want to perform a simple calculation: divide each month's Tax value by its Cost value to find the Percentage. Since there are almost always multiple ways to accomplish the same task, go for a double dip and find two solutions to arrive at the final output.
