check the picture below.
since the arcEF is 75°, then the central angle it is in is also 75°, and the radius is of course 2.4,
[tex]\bf \textit{arc's length}\\\\
s=\cfrac{\theta \pi r}{180}~~
\begin{cases}
r=radius\\
\theta =angle~in\\
\qquad degrees\\
------\\
r=2.4\\
\theta =75
\end{cases}\implies s=\cfrac{(75)(\pi )(2.4)}{180}\implies s=\pi [/tex]
