Design a $4-$bit ALU that performs Arithmetic $($add$,$ subtraction$),$ and Logic operations $($AND$,$ OR$).$The following control signals are to be considered: A$/$S: add$/$subtract $(0$:add, $1$:subtract$)$ A$/$O: AND$/$OR logic functions $(0$:AND, $1$:OR$)$ R$/$W: read$/$write signal $(0$:read, $1$:write$)$