Call Center vs. Support Center

Hi,
I’ve been brought in to run a help desk for a major retail company in the US. My challenge is this: we take approx. 125 calls per day where we’re expected to strive for first call resolution of Layer 1-3 issues as well as server-related problems. I’m looking for guidance on an acceptable SLA in terms of abandon rates, speed to answer, and the staffing necessary to cover 7x19x365. I’m thinking that 5% abandon rates and :30 speed to answer are achievable KPIs. PLEASE let me know your thoughts if you’re in a similar situation.

Thanks,
Aaron