$($a$)$ Using your own memory map, explain what happens when the BSR COUNT instruction is executed at $*$a$.$

$($b$)$ Explain the function of the subroutine COUNT.

$($c$)$ List the contents of D$0,$ D$1,$ and A$7$ when the entire segment of code has been executed.

$($d$)$ Determine the content of A$7($when the entire segment of code has been executed$)$ if the BRA DONE instruction at $*$d is changed to an RTS instruction. Explain your answers in detail.