How to count unique occurances linking two columns

I have three columns. Column A is Firm Name, Column B is Users, Column C is Firm Type. Because of Column B, Column A and C occur more than once. Here is an example:

A, B, C,
Firm A, User 1, Type 1
Firm A, User 2, Type 1
Firm B, User 3, Type 2
Firm B, User 4, Type 2

I'm trying to count how many Firms are Type 1. How can I do that without creating a pivot table?

Thanks.