grammaticality - What type of if-conditional is: “A shop offered us a reduction if we paid in cash.”?

What type of if-conditional is this sentence?

A shop offered us a reduction if we paid in cash.

As far as I know, the only right conditional sentences are these four:

Zero Conditional:

• A shop offer us a reduction if we pay in cash.

First Conditional:

• A shop will offer us a reduction if we pay in cash.

Second Conditional:

• A shop would offer us a reduction if we paid in cash.

Third Conditional:

• A shop would have offered us a reduction if we have paid in cash.

But I cannot tell which of those four it is.