Answer
$7.37\times10^{6} \frac{m}{s^{2}}$
Work Step by Step
First of all, we can convert 0.57 milliseconds (ms) into the unit second (s) as follows and express the answer in $m/s^{2}$
$\frac{4.2\times10^{3} m/s}{0.57 ms} = \frac{4.2\times10^{3} m/s}{0.57\times10^{-3} s} = \frac{4.2\times10^{3}}{0.57\times10^{-3}}\times\frac{10^{3}m/s}{10^{3}s}$
$=\frac{4.2\times10^{6}m/s}{0.57 s} = 7.37\times10^{6} m/s^{2}$
