Answer
$229.34\space m/s$
Work Step by Step
Please see the attached image first.
Let's assume gravitational acceleration $(g) = 9.8\space m/s^{2}$
By using the equation $a=V^{2}/r$, we can find the maximum speed of the jet plane as follows.
$a=\frac{V^{2}}{r}\space =\gt V=\sqrt {ra}$
Let's plug known values into this equation.
$V=\sqrt {8.77\times10^{3}\times0.612\times9.8\space m^{2}/s^{2}}= 229.34\space m/s$
