Please explain thoroughly with a way to check for answers.

Example 5: By increasing its advertising cost s (in thousands of dollars) for a product, a company discovers that it can increase the prot P (in thousands of dollars} according to the mode] P = 253 + 3552 1005 + 200. Then nd the amount s spent on advertising [in thousands of dollars} that maximizes the prot (in thousands of dollars). Find the point of diminishing returns