9.1.5 Double integrals

Problem: Calculate the mass of the plate \( D \) with the density, where \[ D:\left\{\begin{array}{l} \frac{x^{2}}{16}+y^{2} \leq 1 \\ x \geq 0, y \geq 0 \end{array} \quad \mu(x, y)=5 x y^{7} .\right. \]