Find the point of diminishing returns (x,y) for the given function, where R(x) represents revenue (in thousands of dollars) and x represents the amount spent on advertising (in thousands of dollars). R(x) = o.5x3 + 3.6x2 + 7x, 0 5x58 The point of diminishing returns occurs at :|. (Type an ordered pair. Do not round until the nal answer. Then round to two decimal places as needed.)