Speeding + carpool violation=?

I was driving on the 15 south getting on in escondido, SD, and was ticketed for going 90+, the cop wrote that on the ticket, and for being in the capool lane alone (Rancho Bernardo/Lake Hodges). I was in the carpool lane because over by the north county mall there was a sign that said "carpools free" it was about 2 in the afternoon, so not alot of traffic, I thought the sign was saying that the carpool was free for all, like a grace period for that time of the afternoon. Also I have driven in the carpool alone like this many times before and nothing happened. This is the first time I have been pulled over. I'm 22, does anyone know how much the speeding ticket will be, or the cost of the carpool one? Also if I do traffic school what will that help with? Thanks.