$5.$ The $3$D object below is composed of planar surfaces that are either parallel or perpendicular. Answer the following:

$($a$)$ Use Constructive Solid Geometry $($CSG$)$ tree to show how it could be constructed.

$(5$ marks$)$

$($b$)$ Define a possible parametric model for this object and indicate explicit parameters, inexplicit parameters $($if any$),$ and constraints $($if any$).$

$(10$ marks$)$

$($c$)$ Explain how the parametric model could be evaluated.

$(10$ marks$)$