a) See the attached graph. The purple area appears to be what you want to find.
b) Integrating with respect to x seems much easier. If one were to integrate over y, there would need to be two regions of integration: [1, e^2] and [e^2, e^4].
c) [tex] \int\limits^1_0 {(e^{4x}-e^{2x})} \, dx =\frac{1}{4}(e^{4}-1) -\frac{1}{2}(e^{2}-1) \approx 10.2050094588[/tex]
