(b) Given,
$y = 4\cos^{2}{\frac{t}{2}\sin(1000t)}$
$= 2\left( 1 + \cos t \right)\sin(1000t)\ \left( \because 1 + \cos{\theta = 2\cos^{2}\frac{\theta}{2}} \right)$
$= 2\sin{1000t + 2\cos{t\sin{1000t}}}$
$= 2\sin{1000t + \sin{(1001)t + \sin{(999)t}}}$
Therefore, it consists of 3 SHM’s