For the first one, you just multiply 0.05 x 400, which equals 20, so B is your answer.
For the second one, you multiply 0.085 x 1000, which gives you 85, but it says 3 years, so you multiply it to 3, which would be A. 255.
For the 3rd one, you multiply 0.09 x 200, which gives you 18, but it says half a year, so it would be A. 9.
For the last one, multiply 0.12 to 20,000, which is 2400, but it was 3 months, and 3 months is a quarter of a year, so multiply 0.25 x 2400. 0.25 x 2400 = 600, so your answer is B. 600.
Hope this helped you. :)
