At time t$=0$t $=0$t$=0,$ a $4\mathrm{.}21$ kg particle has position vector r$=(7\mathrm{.}00$m$)$i$^(1\mathrm{.}00$m$)$j$^\backslash$vec$\{$r$\}=(7\mathrm{.}00\backslash ,\backslash$text$\{$m$\})\backslash ,\backslash$hat$\{$i$\}-(1\mathrm{.}00\backslash ,\backslash$text$\{$m$\})\backslash ,\backslash$hat$\{$j$\}$r$=(7\mathrm{.}00$m$)$i$^(1\mathrm{.}00$m$)$j$^$ relative to the origin. Its velocity is given by v$=(9\mathrm{.}98$t$2$m$/$s$)$i$^\backslash$vec$\{$v$\}=(-9\mathrm{.}98\backslash ,$ t$^2\backslash ,\backslash$text$\{$m$/$s$\})\backslash ,\backslash$hat$\{$i$\}$v$=(9\mathrm{.}98$t$2$m$/$s$)$i$^$ for ttt in seconds. About the origin with t$=15\mathrm{.}6$st $=15\mathrm{.}6\backslash ,\backslash$text$\{$s$\}$t$=15\mathrm{.}6$s$,$ what are $($a$)$ the particle's angular momentum and $($b$)$ the torque acting on the particle, both in unit$-$vector notation?