We are given with an isosceles triangle having a vertex on the curve given y =<span>27-x^2</span> .
The area of the triangle, A= xy = x (27-x^2)
A' = 27-x^2-2x^2 = 0
x = 3
Amax = 3(27-9) = 54 units2

x equals 25% of the cost.
.25 equals 25%
Therefore x=12
The awnser is $12
Wat r u asking about this problem
x*(1.035) + (4,200-x)*(1.045) = 4,374.00
1.035x + 4,389.00 -1.045x = 4,374.00
15.00 = .01x
x = 1,500 so x (1,500) invested at 3.5% and
(4,200 - 1,500) (or 2,700) invested at 4.5%