I am not very sure about my answer but I will try my bes.
I think you earn 3% of $1200 every year for 5 years.
so 1200 divided by 100 is 12 which is 1% of 1200
12 multiplied by 3 is 36.
so 3% of $1200 is $36.
multiplied by 5 is $180.
you earn $180 interrs over 5 years with an interest rate of 3% from $1200
If the interest rate was increased by 1%, then you will earn a total of 4% interest.
4% of $1200 is 12 times 4 = $48
over 5 years, earning 4% of interest rate, you will earn a total of $240 interest.
If the interest rate is 3%, then over 5 years you will earn $180.
If the interest rate is 4%, then over 5 years you will earn $240.
If the year was increased by 1 then you will earn $36 × 6 dollars which is $216 with a 3% interest rate.
If the year was increased by 1 then you will earn 48 × 6 dollars which is $288 with a 4% interet rate.