Can you provide a summary of the story of Cholkar and his vow to Sai Baba?

The story of Cholkar, detailed in Chapter 15, revolves around a poor man whose job security depended on passing an examination. He made a sincere vow to Sai Baba that if he passed, he would visit Shirdi and distribute sugar candy. After successfully passing, he faced financial difficulties which delayed his pilgrimage. As a personal penance for this delay, Cholkar gave up eating sugar entirely, even taking his tea without it. When he was finally able to go to Shirdi and fulfill his vow, Baba demonstrated his omniscience by specifically instructing that Cholkar be given tea 'well-filled with sugar,' revealing that He was aware of Cholkar's secret sacrifice all along and confirming his faith.