Question: How many teams were represented in the pair of motor races held on 18 and 19 April 2015 at the Bahrain International Circuit in Sakhir, Bahrain?
Sentence (from "2015 Bahrain GP2 Series round"): Haryanto won the second event, a 23-lap sprint race, ahead of Vandoorne in second, and Lazarus driver Nathanaël Berthon in third.
Relevant evidence: No