Answer:
Think of even square roots close to 27: the closest is 25 which has a square root of 5. Now think of the number with an even square root after 25: 36 which has a square root of 6. Since 27 is between 25 and 36, the square root of 27 would be between 5 and 6.
Whenever you face the problem that deals with maxima or minima you should keep in mind that minima/maxima of a function is always a point where it's derivative is equal to zero.
To solve your problem we first need to find an equation of net benefits. Net benefits are expressed as a difference between total benefits and total cost. We can denote this function with B(y).
B(y)=b-c
B(y)=100y-18y²
Now that we have a net benefits function we need find it's derivate with respect to y.

Now we must find at which point this function is equal to zero.
0=100-36y
36y=100
y=2.8
Now that we know at which point our function reaches maxima we just plug that number back into our equation for net benefits and we get our answer.
B(2.8)=100(2.8)-18(2.8)²=138.88≈139.
One thing that always helps is to have your function graphed. It will give you a good insight into how your function behaves and allow you to identify minima/maxima points.
The y intercept is 1.5x+22.7 + the linear equation which is 22
Formula of the area of a triangle:
A = hbb/2
Plug in the numbers.
26 · 26/2
= 338
Therefore, the area of the triangle is 338