Given the amount function A(t) = t² 4t + 48, determine the effective rate of interest during the 6th year.

So we want to find the value of i_6, the effective rate of interest during the sixth year. So we need to find the value at time t=5 and t = 6.

Additional notes:

(from t-1 to t)

i_t = (A(t)-A(t-1))/A(t-1) = (a(t)-a(t-1))/a(t-1) => a(t) = a(t-1)(1+i)

simple Interest: a(t) = 1+it

compound interest:(1+i)^t