A $\backslash (45\mathrm{.}2-\backslash$mathrm$\{$kg$\}\backslash )$ girl is standing on a $149-$kg plank. Both originally at rest on a frozen lake that constitutes a frictionless, flat surface. The girl begins to walk along the plank at a constant velocity of $\backslash (1\mathrm{.}54\backslash$hat$\{$i$\}\backslash$mathrm$\{$~m$\}/\backslash$mathrm$\{$s$\}\backslash )$ relative to the plank.

$($a$)$ What is the velocity of the plank relative to the ice surface?

$$ m$/$s

$($b$)$ What is the girl's velocity relative to the ice surface?

$$ m$/$s