c A plane leaves Los Angeles at \( 23: 20 \) on Tuesday and arrives in Brisbane at \( 7: 15 \mathrm{a} . \mathrm{m} \). on Thursday. What was the length of the flight? (Note that the plat crosses the International Date Line)

1. Los Angeles is on Pacific Time (assume UTC\(-8\)) and Brisbane on Australian Eastern Standard Time (UTC\(+10\)). The time difference is \[ 10 - (-8) = 18 \text{ hours.} \] 2. The plane departs Los Angeles at \( 23:20 \) on Tuesday. Converting this to Brisbane time, we add 18 hours: \[ 23:20 + 18 \text{ hours} = 17:20 \text{ on Wednesday.} \] Thus, when the plane departs Los Angeles at \( 23:20 \) on Tuesday, it is \( 17:20 \) on Wednesday in Brisbane. 3. The flight arrives in Brisbane at \( 7:15 \) on Thursday. So, from the Brisbane perspective, the elapsed time from takeoff in Brisbane time (\( 17:20 \) on Wednesday) to arrival (\( 7:15 \) on Thursday) is computed as follows: - From \( 17:20 \) on Wednesday to midnight (i.e. \( 24:00 \)) is: \[ 24:00 - 17:20 = 6 \text{ hours } 40 \text{ minutes.} \] - From midnight to \( 7:15 \) on Thursday is: \[ 7 \text{ hours } 15 \text{ minutes.} \] - Total flight duration: \[ 6 \text{ hours } 40 \text{ minutes } + 7 \text{ hours } 15 \text{ minutes } = 13 \text{ hours } 55 \text{ minutes. } \] 4. Therefore, the length of the flight is \[ \boxed{13 \text{ hours } 55 \text{ minutes}.} \]