Using the Goal Seek function, how do I complete this problem

Problem 21 We have acquired new furniture for the office. The invoice for $6,000 offers two ways to pay: we can pay the entire amount by Sept 1, or we can pay $3,060 by Sept 1 and $3000 by Jan 1. How does our decision depend on the interest rate at which we can invest our funds?

Initially, to start, you can select a random interest rate. And when you perform goal seek, it will provide you with the rate you need.

Take a look at the formula in cell g15...

It should be the principal times 1 plus the interest rate or in this case... =($G$10x(1+$G$15))

And the formula in the following months should be... previous month's earnings times 1 plus the interest rate. So in case of October... =(G17x(1+$G$15))

When using Goal seek, set cell h18 to a value of 0 by changing $c$15.

Once you correct this, you'll need to run goal seek again.

1 Think of it this way, it would only be better to make payments if we earned more in interest than we would have to pay in service fees. 2 So what we need to find is the "break even point" where Interest Earned is equal to the Service Fee. 3 Any interest rate above that would make the "payment" option attractive. Otherwise, pay it in full. 4 You need to be able to calculate the interest earned for each month so that you can 5 add it up. Then, subtract that from the Service Fee. Set it up like this; Hold your cursor over the cells to read the comments. Sept. 1 Jan. 1 Total Paid Option 1 $6,000 0 $6,000 Option 2 $3,060 $3,000 $6,060 Service Fee $60 Interest Earned Difference Interest Earned Interest Rate Month Earnings Sept Oct Nov Dec Total 6 Finally, use Goal seek to set that difference to $0 by changing the Interest rate. 7 This will give you the interest rate at the break even point described above. 8 State your answer in words below. What option do you choose and why? 1 Think of it this way, it would only be better to make payments if we earned more in interest than we would have to pay in service fees. 2 So what we need to find is the "break even point" where Interest Earned is equal to the Service Fee. 3 Any interest rate above that would make the "payment" option attractive. Otherwise, pay it in full. 4 You need to be able to calculate the interest earned for each month so that you can 5 add it up. Then, subtract that from the Service Fee. Set it up like this; Hold your cursor over the cells to read the comments. Sept. 1 Jan. 1 Total Paid Option 1 $6,000 0 $6,000 Option 2 $3,060 $3,000 $6,060 Service Fee $60 Interest Earned Difference Interest Earned Interest Rate Month Earnings Sept Oct Nov Dec Total 6 Finally, use Goal seek to set that difference to $0 by changing the Interest rate. 7 This will give you the interest rate at the break even point described above. 8 State your answer in words below. What option do you choose and why