Consider a particle whose position is given by the function $f(t)=t^2+9.$

$($a$)$ Find the average velocity $($with units$)$ from $t=1$ to $t=1\mathrm{.}2.$

$($b$)$ Find the average velocity $($with units$)$ from $t=1$ to $t=1\mathrm{.}02.$

$($c$)$ Find the average velocity $($with units$)$ from $t=1$ to $t=1\mathrm{.}002.$

$($d$)$ Estimate the instantaneous velocity $($with units$)$ at $t=1.$

PLEASE HELP ME UNDERSTAND THIS QUESTION $($ALL PARTS A$-$D$)!$ I am stuck on how to do this