SIOUX FALLS, S.D. (KELO.com) — Authorities are offering a reward of up to $5,000 for anyone with information on two armed robberies in Sioux Falls this week. The Bureau of Alcohol, Tobacco and Firearms is offering up the money. An unknown man robbed a Get N Go convenience store on February 13, and two men in ski masks robbed a Super 8 Motel on…