$2-99.$ Position vectors along the robotic arm from $O$ to $B$ and $B$ to A are

$r_{OB}=\{100i+300j+400k\}mm$ and $r_{BA}=\{350i+225j-640k\}mm,$ respectively. Determine the

distance from $O$ to the grip at $A.$

$*2-100.$ If $r_{OA}=\{0\mathrm{.}5i+4j+0\mathrm{.}25k\}m$ and $r_{OB}=\{0\mathrm{.}3i+2j+2k\}m,$ express $r_{BA}$ as a Cartesian

vector.