From t $=0$ to t $=4\mathrm{.}25$ min, a man stands still, and from t $=4\mathrm{.}25$ min to t $=8\mathrm{.}50$ min, he walks briskly in a straight line at a constant speed of $1\mathrm{.}47$ m$/$s$.$ What are $($a$)$ his average velocity vavg and $($b$)$ his average acceleration aavg in the time interval $1\mathrm{.}00$ min to $5\mathrm{.}25$ min? What are $($c$)$ vavg and $($d$)$ aavg in the time interval $2\mathrm{.}00$ min to $6\mathrm{.}25$ min?