Calculate total engine time (cell R2) when the engine mode is ON

Greetings!

I cannot figure out how to calculate total engine time using a formula (the value should be 1.5 hours). If you look at the "Logbook" worksheet, you'll see a "Time" and "Engine Mode" column with information. Basically, I have to calculate the total engine time (cell R2) when the engine mode is ON i.e. engine mode is ON at 8:00 until 9:00, and ON again at 10:00 until 10:30.

Any help on how to approach this would be greatly appreciated!

Thank you.
CC