Pop up menu as text data format problem in multiplication

please provide me formula for this

I work as a multi combination heavy vehicle truck driver. I get paid according to the combination I drive. In my Sheet , I want to apply a formula in Service charges column,

that for combination type column pop up menu

for B double ,services charges = trips kms x .54 $

for semi , service charges = trip kms x.52 $

for rd train , service charges =. trip kms x .56 $