MathNet 2016-part-03 — 184 problems (EN–VI) Question 79

A school program will randomly start between $8{:}30$AM and $9{:}30$AM and will randomly end between $7{:}00$PM and $9{:}00$PM. What is the probability that the program lasts for at least $11$ hours and starts before $9{:}00$AM?