Mysql - How to get the top 5 values from 3 different columns

Hi Exparts,

First of all thanks for taking the time to read my question.

Here's the case I'm a total noob in mysql and I'm learning pretty much by examples, here I want to get the top 5 values from a table based on the number of times a value appears oin three different columns.  Let me put it in 1 example:

Let's say I have a table for people who like cars and in my site they can pick their favorite cars from 3 different brands (ie. Toyota, Honda and Ford).  

Under each brand (by using a dropdown menu) they have all the different cars from each brand...  for honda for example they will have civic, accord, CR-V, etc.  After submitting the form this information is saved in the database under the brand rows

The table is users and the columns for each row are ID, username, b_Ford, b_Honda and b_Toyota.

So the actual data would look like this:

1, john,  Civic, Explorer, Corolla
2, james, accord, fusion, corolla
3, Lynda, civic, focus, corolla
4, Bryan, civic, focus, corolla

I need help writting a query that will give me the top 5 favorite car accorss all different brands selecting the values from b_Ford, b_Honda and b_Toyota.

In the case of this example the output would be as follows

Corolla (4)
Civic (3)
Focus (2)
Accord (1)
Fusion  (1)

I managed to get the top 5 from each brand using SELECT b_Ford, COUNT(*) FROM users GROUP BY b_Ford;

But I actually need the top 10 across all different brands.

Can you Help?  

Thanks in advance.