Find the Area of the Region Bounded by the Given $y=\cos x, y=\sin 3 x, x=0, x=\frac{\pi}{2}$

Multiple Choice

Find the area of the region bounded by the given curves. $y=\cos x, y=\sin 3 x, x=0, x=\frac{\pi}{2}$

A) $\frac{1}{4}$
B) $\frac{1}{2}$
C) 4
D) 2
E) $\frac{1}{3}$