Figure $5\mathrm{.}7$ shows a simple microwave oven. Draw an STD that captures the behavior described by the following description as follows.

$($a$)$ The Open button opens the door, stops cooking, and holds time.

$($b$)$ The Clear button clears the timer. If cooking was active, it is disabled.

$($c$)$ The Start button starts cooking for whatever time has been set. While cooking, the timer decrements to zero and turns off cooking when it reaches zero.

$($d$)$ The Popcorn button forces a time of $2$ minutes to be set into the timer.

$($e$)$ The Def$/$Light button forces the power level to $50\%.$

$($f$)$ Time is set by twisting the dial and then pressing the button at the center of the dial. No action takes place until the button is pressed. At that point, the time on the dial is entered into the timer.

$($g$)$ There is a switch connected to the door to show whether it is open or closed.