Is there a formula to return data dependant on data submitted in 3 different Cells?

[Nats123]

Can Anyone help me??

Im looking to put in a formula for a mileage claim form.
The form has the vehicle type, fuel type & capacity and depending on what you drive depends on the amount you can reclaim so I want the mileage rate to default automatically once those 3 cells are filled in.
Also if you have a passenger you get an extra 5p per passenger per mile so ideally Id like to encorporate this into the formula.

Apologies if this is a really basic formula, Im self taught on formula's so this one is just getting me a bit confused.

Any help will be greatly received