Answer ASAP and show all work with legible handwriting please for business algebra

Next question You Find the point of diminishing returns (x,y) for the function R(x), where R(x) represents revenue (in thousands of dollars) and x represents the amount spent on advertising (in thousands of dollars) R(x) = 10,000 - x3+ 39x2+ 800x, OSX s 20 The point of diminishing returns is (Type an ordered pair.)