<human>: Here is a goal: How can you rapidly calculate a 20 percent tip?

How would you accomplish this goal?

OPTIONS:
- Take the total of the bill and move the decimal point one place to the left, double that number and that is 20 percent.
- Take the total of the bill and move the decimal point one place to the right, double that number and that is 20 percent.
<bot>: Take the total of the bill and move the decimal point one place to the left, double that number and that is 20 percent.