Agriculture Feinerman and colleagues $^{15}$ created a mathematical model that related the yield response of corn to nitrogen fertilizer was given by the equation $y=-5.119+$ $0.099 x-0.004 x^{1.5},$ where $y$ is the yield measured in tons per hectare and $x$ is in kilograms per hectare. Use calculus to find the value of $x$ that maximizes yield.