Help getting total on quote from line items

[Hypnotech03]

So I am trying to create an ordering / invoice app
I have an order form with
Employee name (can add or select pre existing)
customer name (can add or select pre existing)
Vehicle details (can add or select pre existing)
Select service (all pre existing,[interior][Performance] etc)
Select line items dependant on service selected (like engine upgrade, turbo, transmission for [Performance]
Each line item needs a price input (difference price for each vehicle type)

From these details above I want at the bottom of the Order page to have a total cost of selected line items.
Then total X 140% = customer price.

I have most of the collections & data in the system.

It’s just getting them working right is where I’m getting stuck.
Any help would be appreciated.

Right now I have a total off ALL line items on the database.