How to provide different special price for weight option

Hello,
I have a product with values as follows ;
For 250gms : actual price is 192 , special price is 160 here we save 32 rs
500gms : actual price is 252 , special price is 210 here we save 42 rs
1 kg : actual price is 444, special price is 370here we save 74 rs

suppose we have given special price for 250 gm den it takes 32 rs in all options

demo for this type is on https://www.sweetkadai.com/cakes/79-plum-cake.html

We have radio button options for weight.
Wehen we give special price to products it keep same to all options.
how can we solve this in opencart