In Exercises 27-32, sketch the region of integration and evaluate the
integral.
27. $\int_{0}^{\pi} \int_{0}^{x} x \sin y \, dy \, dx$
28. $\int_{0}^{\pi} \int_{0}^{\sin x} y \, dy \, dx$
29. $\int_{1}^{\ln 8} \int_{1}^{\ln y} e^{x+y} \, dx \, dy$
30. $\int_{1}^{2} \int_{y}^{y^2} dx \, dy$
31. $\int_{0}^{1} \int_{0}^{y^2} 3y e^{xy} \, dx \, dy$
32. $\int_{0}^{4} \int_{\frac{3}{2}}^{\sqrt{x}} e^{y/\sqrt{x}} \, dy \, dx$
