Given a process as shown in figure $($a$)$ and the ladder logic program as in figure $($b$).$ Notice the highlighted instructions.

$($a$)$ Is a normally open or closed switch assumed for STOP?

$($b$)$ Refer to switches, sensors and lights in figure $($a$),$ explain how the system works.

$($a$)$ Sketch of the process

$($b$)$ Control logic