5^2 x 3.14 = 78.5
78.5 ÷ 2 (cuz it's a half circle) = 39.25inches
i need more info. are you looked to see there mph? how much they deliver? how far they go?
we are told that the revenue is
this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.
so in this case, we have a=−10 and b=4080, so the x-value of the vertex is