what will happen to me if this is my first offense

What is the name of your state?Washington

I was accounted for arson and burglary 2nd degree then when I was booked into the detention center and went to my first court date they accounted me for burglary 2nd degree and this is my first offense also I got court on june 29th 2004 the reason for all this I was with some people that were breaking into a community center and burning some paper towls in there while I was outside. So what would be my sentence

RCW 9A.52.030
Burglary in the second degree.
(2) Burglary in the second degree is a class B felony.

RCW 9A.20.021
Maximum sentences for crimes committed July 1, 1984, and after.
(b) For a class B felony, by confinement in a state correctional institution for a term of ten years, or by a fine in an amount fixed by the court of twenty thousand dollars, or by both such confinement and fine;

For addition information:
http://www.leg.wa.gov/RCW/index.cfm?fuseaction=title&title=9A