The answer for this question is 80
THE ANSWER ABOVE IS INCORRECT!! If you are doing Apex, the answer is doubling a cube. It can't be done with a straightedge or compass so it is impossible and was believed to be Apollo wanted something of his doubled with was a cube.
The Answer is that the present value of $100 is $100. Because this $100 dollar is deposited today so the time is equal to zero and when time is zero the value of amount is the value of amount itself.