Definition: In this task, you're given a question, along with a context passage. The passage will not have a direct answer to the question, but can include some information and a clue for the answer. Assuming you can only obtain information about one entity in the passage, your job is to determine whether information from the passage can be used to answer the question. Indicate your choice as `a` for Yes or `b` for No.
Input: Question: What was the name of Stephen's paternal grandfather? Passage:Stephen Tvrtko I (, Стефан/Стјепан Твртко; 1338 – 10 March 1391) was the first King of Bosnia. A member of the House of Kotromanić, he succeeded his uncle Stephen II as Ban of Bosnia in 1353. As he was a minor at the time, Tvrtko's father, Vladislav, briefly ruled as regent, followed by Tvrtko's mother, Jelena. Early in his personal rule, Tvrtko quarreled with his country's Roman Catholic clergy, but later enjoyed cordial relations with all the religious communities in his realm. After initial difficulties – the loss of large parts of Bosnia to his overlord, King Louis I of Hungary, and being briefly deposed by his magnates – Tvrtko's power grew considerably. He conquered some remnants of the neighbouring Serbian Empire in 1373, after the death of its last ruler and his distant relative, Uroš the Weak. In 1377, he had himself crowned King of Bosnia and of Serbia, claiming to be the heir of Serbia's extinct Nemanjić dynasty.


b