a) Tiffany deposits $12 into an account at the end of each day in 1989 and 1990 and $15 at the end of each day in 1991. The account earns an annual effective interest rate of 9% in 1989 and 1990 and an annual effective interest rate of 12% in 1991. Find the amount in Tiffany’s account on December 31, 1991. (Answer: $16,502.58)

b) Rework part (a) using the approximation that the deposits are made continuously. (Answer: $16,504.75)

I think I'm pretty close, just missing something somewhere. I have

12[(1.000236)^730 - 1 / .000236] + 15[(1.000311)^365 - 1 / .000311]

= 15355.5

(because (1+j)^4=1.045 and (1+j)^4=(1.025)^5)

And also I'm not sure for part (b) how you would work it out differently if the deposits are continuous.

Thank you!