I have a request concerning calculating with the form.
Here is the scenario:
i have a product with a set price 100$
the user can then add multiple option with checkboxes, but the first three are free. Every checked checkbox after the 3rd checked checkbox shall add another 100$
and the sum shall be shown accoding to the amount
for example:
user checks 2 boxes
the sum would be 100$
user checks 3 boxes sum still be 100$
user checks 6 boxes sum would be 400$ (three are included the additional three cost 100$ per checked box)