Ibrahim started at 9:30 PM from his house to go to Toki's house. When he reached there, he saw it was 8:55 PM in Toki's clock. He started to back towards his house when it was 9:00 PM at Toki's. He reached at his house when it was 10:15 PM in his clock. If Ibrahim needed equal time to go and come back, find out the number of minutes Toki's clock is slow by.