1) montly rate, r = 5% / 12 = 0.416% = 0.00416
2) capital, C = $ 450 = present value
3) time = 11 years => number of periods = 11 * 12 = 132
4) Formula: FV = C * (1 + r) ^ (number of periods)
5) Calculation: FV = $450 * ( 1 + 0.00416)^(132) = $ 779.07
Answer: $ 779.07
I cannot do turning points.
Also, if this is from a test, it can be removed.
But here is a graph of the function.
It would take 4 days for them to build the houses.