How can I amend the below code to add additional materials to the LISP - autocad-plugin

Question

I am new to coding but very eager to learn. I am attempting to edit this existing LISP to add additional materials to the list. Currently when I run the LISP it only has Aluminium as an option to select. I would like to add additional materials and weights to suit. I also would like to know how to change the weight settings from LBS/FT to Kilograms & Meters.
Any help would be hugely appreciated.
;;; Lisp function for calculating weight with choice to assign material for selected:
;;; 2d shape - expressed in pounds per foot lenght - lbs/ft.
;;; or
;;; 3d solid - expressed in Pounds - lbs
(defun C:Wt (/ area volume en ent obj ospace prefix pt remd resp suffix suffix1)
;;local defun
(defun density (mat)
(cond ((eq "Aluminium" mat) 0.0972) ;<--lb/in³
;; add other materials density similarly
(T nil)
)
)
(defun matname (mat)
(cond ((eq "Aluminium" mat) " mat: Aluminium")
;; add other materials names similarly
(T nil)
)
)
;;main part
(setvar "dynmode" 3)
(setvar "dynprompt" 1)
(setq ospace (vla-get-block
(vla-get-activelayout
(vla-get-activedocument
(vlax-get-acad-object)
)
)
)
)
(setq prefix "Weight="
suffix "lbs/ft."
suffix1 "lbs"
)
(setq ent (entsel "\nSelect a object:"))
(setq en (car ent))
(if (wcmatch (cdr (assoc 0 (entget en)))
"REGION,*POLYLINE,CIRCLE,ELLIPSE"
)
(progn
(setq obj (vlax-ename->vla-object en))
(initget
"Aluminium"
) ;<-- add other materials here
(setq resp
(getkword
"\Choose material [ALuminium] <AL>: "
)
)
(setq area (strcat prefix
(rtos (* (vla-get-area obj)
(density resp)
)
3 ;<-- inches
4 ;<-- precision
)
suffix
(matname resp)
)
)
(setq pt (getpoint "\nPick text point: "))
(vla-addtext
ospace
area
(vlax-3d-point (trans pt 1 0))
(getvar 'Textsize)
)
)
)
(princ)
(if (wcmatch (cdr (assoc 0 (entget en))) "3DSOLID")
(progn
(setq obj (vlax-ename->vla-object en))
(initget
"Aluminium Steel SS316 Glass Rubber Silicone Plastic Granit Marble"
) ;<-- add other materials here
(setq resp
(getkword
"\Choose material
[ALuminium/STeel/SS316/GLass/RUbber/SIlicone/PLastic/GRanit/MArble] <AL>: "
)
)
(setq volume (strcat prefix
(rtos (* (vla-get-volume obj)
(* (density resp) 0.001)
)
2 ;<-- metric
5 ;<-- precision
)
suffix1
(matname resp)
)
)
(setq pt (getpoint "\nPick text point: "))
(vla-addtext
ospace
volume
(vlax-3d-point (trans pt 1 0))
(getvar 'Textsize)
)
)
)
(princ)
)