Auto Fill Formulas into Google Form Submissions (google sheets automation)

The Example: I am making a basic margarita pizza for a client; the client wants toppings at extra charge. The client uses a google form to register their request; the form collects all relevant information, adds the extra toppings and generates a bill/invoice at the click of the submit button. The Objective: To configure an existing spreadsheet that can accept data inputs from an external google form without losing any formulas. The spreadsheet to be able to calculate the total cost(s) of the pizza (service), add additional toppings (add-ons) by itself, then generate an invoice (PDF) which is automatically sent directly to the client's email address. The Mission: To tweak an existing spreadsheet so that it can automatically process the data captured within a linked google form. It will be able to calculate a basic service but then have the flexibility to accept up to 4 additional services (toppings) IF requested in the form. The spreadsheet will automate the data as captured by the form. The Fee: £10 - for a couple of formulas to complete the worksheet. No timewasters, please.