Establish and produce X-class products. Then the profit is (8+2 * (x-1)) * 60 * (1-(x-1) * (0.03).

simplify

(8+2 *(x- 1))* 60 *( 1-(x- 1)*(0.03))

=(6+2x)*60*( 1.03-0.03x)

=60*(6. 18-0. 18x^2+2.06x-0.06x^2)

=60*(6. 18-0.24x^2+2.06x)

Then it is obvious to find the maximum value of (6. 18-0.24x 2+2.06x) in10.

Then find the two zeros of this equation, find the middle line, and then draw an image, and it will come out.

Finding zero and midpoint won't help you. This is a function image, and the fourth grade has the highest profit.