Muchausen was told to find the number of soldiers in the enemy's camp.  He flew to the enemy's camp very quickly on a cannonball then returned on foot.  The round trip took 1 hour and 10 minutes.  To make sure he counted soldiers correctly, he made a second trip.  This time he traveled on a cannon ball to the enemy's camp and returned at the same speed by jumping on a cannonball as it was fired from the enemy's camp.
The round trip took 20 minutes.  How much time would Muchausen spend if he walked?