Those who are or had rented an apt.

Since there four names on this lease, will it be possible if the ammount is divided by four,

It depends on the TYPE of lease you signed.  It should be explicit in the lease if all signed parties are equally 100% responsible... I had a lease like that and when my roommate skipped out and let her rent check bounce, I had to pay the difference because I was 100% responsible (as was she, although she was gone.)  Other lease types will say the tenants are proportionally responsible - ie, 25% to each of the 4 roommates.  It's less likely you have that type of lease - most landlords want the most accountability they can get.
 
Check out the laws in CA for your rights and your landlord's obligations to report the problems or return the deposit.  I suspect that friend has been contacted well before now, so don't let the 9months fool you (but the landlord would have to provide proof that he's tried to contact all of you within whatever legal timeframe is allowed.)  I also would NOT respond to ANYONE until I knew my rights and obligations first.  Once you know what you're legally obligated to, then contact the property management company directly.  Be warned that your ex-roommate may be ignoring the landlord and is trying to get you to take the fall for it ALL. 
Landlords go through this all the time, so don't expect much leniency.  It's a business and they want as much money out of it as they can get.  But you should know what they're legally intitled to at this point.  Ugh - good luck!

Bring a printed version of the site I put down. That right there is the law in California. They can't deny that, and all they can do is come up with proof that a letter was sent in 21 days after move out. If they don't have proof right then and there, tell them you won't give them any money. Because legally, they didn't do it correctly.
 
If they try to tell you that they can't find the letter, blah blah blah, it's BS. They can type one up right on the spot after you leave and tell you that they found it the next day. If it's been a year or so, and they do show proof right away of a letter being sent. Tell them to show you receipts, and documents of the so called work being done.
 
Don't let them sucker you into paying anything without proof of that letter.

By the way, you can contest charges against your credit report....

 
Make sure the amount owed is worth fighting for...getting things off your credit report can take months (sometimes years) and cost you a load of money in the process.  Once it hits your credit report it is a huge pain. 
 
I have come to learn that a few hundred bucks, and in some cases a few thousand is hardly worth all of the waisted time in the end.

Thanks Hlb118, the link you provided is very helpful and  I will print that out and bring it to the office. I'm stress and paranoid right now, Hopefully this issue is resolve, and i don't need to deal with all those people again.
Thanks everyone for the helpful responses.