Answer
$\approx$1040 mi/h
Work Step by Step
Suppose a point moves along a circle of radius $r$
and the ray from the center of the circle to the point
traverses $\theta$ radians in time $t$.
Let $ s=r\theta$ be the distance the point travels in time $t$.
The angular speed of the point is $\omega=\theta/t$.
The linear speed of the point is $v=s/t$.
$ v=r\omega$.
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1 revolution = $ 2\pi$ radians.
23h 56min 4s =$23+\displaystyle \frac{56}{60}+\frac{4}{3600}$ h$= 23.9344$ h
$\displaystyle \omega=\frac{\theta}{t}=\frac{2\pi\ rad}{1\ day}\cdot\frac{1\ day}{23.9344\ h}=\frac{2\pi}{23.9344}$ rad/h
$ v=r\displaystyle \omega=\frac{3960\cdot 2\pi}{23.9344}\approx$1039.56705898 mi/h
$\approx$1040 mi/h
