Final answer:
To calculate a rewards program incentive, you should use the percentage of a number. Simple interest formula is not used for rewards program calculations; instead, you apply the reward percentage to the total accumulated points or amount.
Step-by-step explanation:
To calculate a rewards program incentive, the correct method is to use the percentage of a number. This is because rewards programs typically offer incentives based on a certain percentage of the amount you have spent or accumulated in points. 
For example, if you have earned 1,000 points in a rewards program and the program offers a 5% cashback incentive, you would calculate your reward by taking 5% of 1,000 points.
Simple interest is a different concept used in finance to calculate the interest on a principal amount over time. The formula for simple interest is Interest = Principal x Rate x Time, which is not suitable for calculating rewards program incentives.
Therefore, to calculate how much incentive you will receive, you would use the following steps:
- Identify the percentage of the reward offered by the program.
- Find out the total number of points or amount eligible for the reward.
- Calculate the incentive by multiplying the eligible points or amount by the reward percentage.
Using the example above, the calculation would be:
1,000 points x 0.05 (5%) = 50 points
So, in this case, the reward is 50 points.