Let's start with the length. All you need to do is multiply is by 1/500.
You could also find the decimal equivalent to 1/500.
1/500= .002
200×.002= .4
So length of the model is .4 ft.
The width:
.002×140=.28
The width of the model is .28 ft.
The length of the model is .4 ft and the width of the model is .28 ft.