He didn’t want to wake up the sleeping pills.

Send the box with a lock attached and locked. Your friend attaches his or her own lock and sends the box back to you. You remove your lock and send it back to your friend. Your friend may then remove the lock she or he put on and open the box.

In the back. See, the train is still accelerating as it is leaving the station so the train will be moving faster when the back of the train enters the tunnel.

A dollar in pennies.