12. I have worked this one few times but keep receiving an incorrect, where is my calculation mistake?

- 1200x A firm has the marginal-demand function D'(x) = ", where D(x) is the number of units sold at x dollars per unit. Find the demand function given that D = 13,000 when x = $4 per unit. 25- x2 13,000 The demand function is D(x) = 25-x