#### Answer

(a) $5\pi$ radians
(b) $\frac{8\pi}{3}$ radians

#### Work Step by Step

(a) Since 1 circular orbit is equal to $2\pi$ radians, $2.5$ orbits are equal to $2.5\times2\pi=5\pi$ radians.
(b) Since 1 circular orbit is equal to $2\pi$ radians, $\frac{4}{3}$ orbits are equal to $\frac{4}{3}\times2\pi=\frac{8\pi}{3}$ radians.