Can you describe the story of Cholkar, his vow, and his experience with Sai Baba?

The story from Chapter 15 details the experience of a man named Cholkar, whose job security depended on passing an examination. He made a vow to Sai Baba that if he passed, he would distribute sugar candy in Baba's name. After his wish was granted, financial hardship, described as a difficult 'threshold-ghat', delayed him from fulfilling the vow. As a personal penance during this delay, Cholkar gave up sugar entirely. When he finally reached Shirdi and fulfilled his promise, Baba demonstrated his omniscience by telling another devotee, Jog, to serve Cholkar 'cups of tea, well-filled with sugar,' which amazed Cholkar and confirmed Baba's awareness of his secret sacrifice.