Part (a)
You are correct in choosing "Each dollar spent appears to earn the same number of points"
You are also correct in stating that spending $10 will earn 100 points.
This is because each $1 will get you 10 points.
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Part (b)
The first column says 2 customers need 6 minutes. Divide both of these values by 2 to get 1 customer needing 3 minutes. In other words, it's 3 minutes per customer.
Follow the same steps for the second column. We have 6 customers needing 18 minutes. Divide both parts by 6 to end up with the "1 customer needing 3 minutes" again. The same will happen with the last column as well.
No matter which column you pick, the rate is 3 minutes per customer.
So you'll select the second option which says "It appears to take the same amount of time to serve each customer"
To predict how many customers can be served in 27 minutes, divide that by 3 to get 27/3 = 9. We predict 9 customers will be served in this timeframe.