Four deposits are made in all. 1st deposit gets 4 years' compound interest, the 2nd gets 3 years', the 3rd 2 years' and the 4th one year's. The sum is effectively 600(1.05^4+1.05^3+1.05^2+1.05). Each term of this sum gives the total amount accumulated for each amount deposited, and the total sum is the final balance of the account.
1st deposit accumulates 729.30375
2nd deposit accumulates 694.575
3rd deposit accumulates 661.5
4th deposit accumulates 630
The total is 2715.37875 or $2,715.38 to the nearest cent. These figures assume that every deposit is made to accumulate at least one year's interest. That means that the fourth deposit at the end of the year stays in the account for twelve months and gains interest for one year.
