I have a table like this:

id car state regdate
===========================
1 toyota good 2006-04-01
2 toyota good 2006-04-05
3 ford bad 2006-05-25
.....

the state column is ENUM ('good','bad','very bad')

given a car name (lets say toyota), I want a query that returns the
number of 'good', 'bad' and 'very bad' cars registered for each month
like this:

month good bad very bad
april 2006 2 0 0
may 2006 1 1 2
.....

How can I do that?