Who was the Nawab of Bengal at the time of the Battle of Buxar (1764)?

The Battle of Buxar was fought on October 22, 1764, between the British East India Company and a combined alliance consisting of Mir Qasim (the deposed Nawab of Bengal), Shuja-ud-Daula (Nawab of Awadh), and Mughal Emperor Shah Alam II. However, at the time of the active military engagement, the British had already officially reinstated Mir Jafar as the Nawab of Bengal (reigned 1763–1765).