Students in your class are continuing to model the motion of Triton $($one of Neptune's $13$ moons$)$ around Neptune, but now using VPython. The code your class has received contains the following snippet of VPython code.

from visual import $*$

Neptune $=$ sphere$($pos$=$vector$(100,200,300),$ radius$=1,$ color$=$color.blue$)$

Triton $=$ sphere$($pos$=$vector$(10,20,30),$ radius$=2,$ color$=$color.white$)$

$($a$)$ From this snippet, which of the following lines of code might your group write to describe the separation vector pointing from Neptune to Triton in VPython?