MaxScript help !!!

Write a script that adds the functionality to the "Lec 2 Demo" utility that we started in class. The "red box" button creates a red box of default dimensions somewhere on the x-y plane. The "Yellow Box" does the same thing except that the box color is yellow. When a person presses the "Delete" button, the utility should delete objects according to the option set in the radiobuttons.
that my code :
utility utDemo "My First Utility"
(
Button btnMakeRedBox "RedBox" toolTip:"Make a Box" \ -- red button
align:#Left Width:70 across:2
Button btnMakeYellowBox "YellowBox" toolTip:"Make a Yellow Box" \-- Yellow button
align:#Left Width:70 across:2

RadioButtons rdoDelete "Remove..."\
labels:#("boxes only", "Everything except boxe","all")\
default:1 columns:1

button button3 "Delete Now" -- delete button

local b, c= classof != b


on spinnerExample open do
(
s=undefined
)

--button RED box handler
on btnMakeRedBox pressed do
(
b=box wirecolor:[255,0,0]

)
--button Yellow box handler
on btnMakeYellowBox pressed do
(
b=box wirecolor:[255,255,0]
--b.pos = [0,0,1]

)

--button3 Delete handler

on button3 pressed do
(
if (rdoDelete.state == 1) then
delete b
if (rdoDelete.state == 2) then
delete c
)
)

I have problem with RadioButtons
where use RadioButtons and delete button