Answer: 3 hours 15 minutes, because all the preparation times add to 3 hours and 15 minutes
Explanation:
Since, The astronaut will begin preparation from the time when the preparation on the base starts,
Thus, his total time = Time in preparation on base + Time in travelling to the launch pad + Time in pre-launching check once in the space craft.
= 2 hours 15 minutes + 20 minutes + 40 minutes
= 3 hours 15 minutes.
Thus, he should begin preparation before 3 hours 15 minutes.