What happens to the area of a parallelogram if the height doubles but the base is unchanged? if the height triples? if the height is 100 times the original

This stem-and-leaf plot represents the heights of the students on ralph's basketball team. one student's height is missing from the plot. if the mean height of all the students on the team is 61 inches, what is the missing height? a. 55 in. b. 59 in. c. 61 in. d. 65 in.

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Ineed with math stuff it involves graphs