Riddle time! Win A VOUCH!

There were two mathematicians who met at a conference in Nice a year, their name was Mark and Chris. They attended the same university several years ago, and they have not met since then. After this conference they met in the entry hall of the hotel. They talked together, and eventually asked Mark about how many children Chris had. He replied that he had three children. Nils would also know how old the three child was, but since both of them were mathematicians Chris said:

- If you adds up to the age of my children then the number is 13
- I also noticed that if you multiply the age of my three children, then you will get your room nummer in this hotel.

They each went to their rooms, but Mark was still not completely satisfied. When they met again Mark asked:
- "I must have some information to know the age of the three kids," he said.
- "Yes, that's right!" My oldest child is born in New York ", Chris answered.
- "Ahh, then I know the age of your children," Mark said.

How could Mark find out about the childrens age?
please post a solution so i know that you guys did not cheat0rz

Good Luck

 

Umm.. vouches cant be used as a prize/currency =3

 

Vouches aren't currency...