(a) The major arc angle is \(2\pi-\pi/3=5\pi/3\). The outer straight sides each have length \(r\), so \[L=\left(\frac{5\pi}3+2\right)r.\]

(b) \[r=\frac{200}{2+5\pi/3}=27.63962665\ldots\text{ cm}.\] The major sector area is \(5\pi r^2/6\), and rhombus area is \(r^2\sin(\pi/3)=\sqrt3r^2/2\). Thus \[A=\left(\frac{5\pi}6+\frac{\sqrt3}2\right)\left(\frac{200}{2+5\pi/3}\right)^2=2660\text{ cm}^2\quad(3\text{ s.f.}).\]