In the mid-1800s, settlers would often plan to depart with how many days’ worth of supplies before they would need to restock?

The picture below shows president richard nixon and the first lady standing before the great wall of china in 1972. they are smiling - as are the chinese with them. when this picture was shown on american television, americans were aware that it was a historic moment. what are two reasons why this moment was important for both china and the united states?