Rug price (area + perimeter with variable border)

Hi!

I’m developing a rug e-commerce.
I need to be able to calculate the price of the area of the rug plus the price of the border.
I was able to make the area:
https://dronodata.net/tapetes/produto/torino-retangular/
And now I’m asking for your help with the area plus the border.
We have 4 options for the border (with different prices).
Work in progress:
https://dronodata.net/tapetes/produto/torino-retangular-rebordo/
Can you show me the right path?

Thanks!