Can you narrate the story of Cholkar and the vow he made to Sai Baba?

The story of Cholkar, found in Chapter 15, details a poor man who depended on his job. To make his salary permanent, he needed to pass an examination. He made a vow to Sai Baba that if he passed, he would travel to Shirdi and distribute sugar candy in Baba's name. By Baba's grace, he passed, but financial hardships, referred to as the 'threshold-ghat' of home expenses, delayed his journey. As a personal penance during this delay, Cholkar gave up sugar completely. When he finally reached Shirdi and fulfilled his vow, Baba revealed his omniscience by telling a host to give Cholkar tea 'well-filled with sugar,' confirming that He was aware of Cholkar's secret sacrifice all along.