Please give an example $($i$.$e$.,$ draw a layout of four nodes A$,$ B$,$ C$,$ and D$)$ of a three$-$sender hidden$-$node collision $(3\mathrm{.}7\mathrm{.}1\mathrm{.}4$ Hidden$-$Node Problem$)$; that is$,$ three nodes A$,$ B and C$,$ no two of which can see one another $($i$.$e$.,$ A cannot see B or C; B cannot see A or C; C cannot see A or B$),$ where all can reach a fourth node D$.(2$pts$)$ Can you do this for more than three sending nodes? $(1$ pt$)$ How? $(1$ pt$)$