A student holds a ruler between their thumb and index finger, suddenly releases it$,$ and then as fast as possible, captures it again, measuring the distance it has dropped. they repeat this procedure four additional times, finding drops of $\mathrm{.}28,\mathrm{.}24,\mathrm{.}30,$ and $\mathrm{.}31$m$.$ what is the student's average reaction time, and what is the standard deviation of those times.