The graph shows the profitP(in thousands of dollars) of a company in terms of its advertising costx(in thousands of dollars). (Round your answers to the nearest whole number.)ThexP-coordinate plane is given. The horizontal axis is labeledxand Advertising cost (in thousands of dollars) and the vertical axis is labeledPand Profit (in thousands of dollars).

• The curve begins at approximatelyP= 400on theP-axis,goes up and right becoming more steep, passes through the point(20, 2,000),goes up and right becoming less steep, changes direction at the approximate point(40, 3,600),goes down and right becoming more steep and exits the window at approximatelyx= 61on thex-axis.
• The curve goes through the approximate points(0, 400),(10, 800),(20, 2,000),(30, 3,200),(40, 3,600),(50, 2,900),and(61, 0).

(a)Estimate the interval on which the profit is increasing. (Enter your answer using interval notation.)

(b)Estimate the interval on which the profit is decreasing. (Enter your answer using interval notation.)

(c)Estimate the amount of money the company should spend (in dollars) on advertising in order to yield a maximum profit.$ (d)Estimate the point of diminishing returns.

(x,P) =