Plz give detailed ans..aling with the frmula used

Dear student,
Please find below the answer:

The correct option is (1).
Contribution of each gene= Maximum height- Minimum height/ No. of genes
                                         = 12-8/4 = 1
Contribution of dominant genes in plant having genotype AaBb= 1 x 2= 2
Height of the plant with genotype AaBb= 8 +2 +2 = 12 cm (Maximum expression)
                                         
Hope this information clears your doubt.
Regards.