The table shows interest owed for a home improvement loan based on how long it takes to pay off the loan.

a. How much more interest is owed on $900 (ignore the AED) for 9 months than for 6 months?

b. Does the interest rate increase at a constant rate?

(Please answer quick! Don't go to other answers and copy and paste or put something that isn't even about this, I really need help! Thank you.)