Question 10
My twelve-hour digital clock has four digits, two of which represents the hour and the other two represents the minutes. The minutes are shown with leading 0s, but the hours are not. Upside down, the digits 0, 1, 2, 5, 6, 8 and 9 are read as 0, 1, 2, 5, 9, 8 and 6 respectively. One day, I made a phone call on a scheduled time, and learned that it was too early. Then I realized that I had read the time on the clock upside down. If you know by how much time I called early, you will know what time I made the call. What time should I have made the call?