308 Maximum Horsepower That Can be Transmitted by Steel Shaft

$12(1000) = \dfrac{16T}{\pi (2^3)}$

$T = 18\,849.56 \, \text{lb}\cdot\text{in}$
 

$T = \dfrac{P}{2\pi f}$

$18\,849.56 = \dfrac{P(396\,000)}{2\pi (240)}$
$P = 71.78 \, \text{ hp}$           answer