Determine the amount that must be deposited now at compound interest to provide the desired sum for each of the following:

1. Amount to be invested for 10 years at 6% per annum, compounded semiannually, to equal $17,000.

2. Amount to be invested for 21/2 years at 8% per annum, compounded quarterly, to equal $5,000.

3. Amount to be invested for 15 years at 12% per annum, compounded semiannually, then reinvested at 16% per annum, compounded quarterly, for five more years to equal $25,000.

4. Amount to be invested at 8% per annum, compounded semiannually for three years, then $5,000 more added and the entire amount reinvested at the same rate for another three years, compounded semiannually, to equal $12,500.