An angle such as $\frac{?}{{?}_{A}BC}$ is called an inscribed angle and it can be proved that the measure $($in degrees$)$ of an inscribed angle is half the measure $($in degrees$)$ of the arc it cuts.

If the circumference of the circle is $30$ inches and the length of arcAC is $4$ inches, then what is $\frac{m}{{?}_B}?$

$\frac{m}{{?}_B}=$

$($Type an integer or a decimal.$)$