$7)[13$ points$]$ Suppose there are two ISPs providing WiFi access in a particular tearoom, with each ISP operating its own AP with its own IP address block.

$($a$)$ Suppose that by accident, each ISP has configured its AP to operate over channel $11.$ Whether the $802\mathrm{.}11$ protocol will be broken down in this setting scenario? And what will happen if both APs try to transmit at the same time? $(8$ points$)$

$($b$)$ Suppose the two APs operate at two different channels, e$.$g$.,$ one AP operates over channel $1$ and another AP operates over channel $11.$ What will happen if they transmit at the same time? $(5$ points$)$