$\backslash$table$[[,$Allocation,Request,Available$],[,R_1,R_2,R_3,R_4,R_1,R_2,R_3,R_4,R_1,R_2,R_3,R_4,,,,,,,,,,,],[A,1,0,1,1,0,1,0,0,0,0,0,0,,,,,,,,,,,],[B,1,1,0,0,0,1,1,0,,,,,,,,,,,,,,,],[C,1,0,1,1,0,0,0,0,,,,,,,,,,,,,,,],[D,0,0,0,0,1,0,1,0,,,,,,,,,,,,,,,]]$

Is the system in a deadlock state? If the system is in a deadlock state, list all processes that involve in a deadlock. Show your computation step$-$by$-$step; $($Marks will be earned for showing how the answer was derived$).$

$3.$ What are monitors and condition variables?

$(4)$

$4.$ List the four necessary conditions for deadlocks.