Why did it depress Holden when an "old guy" told him that his days at Pencey were the happiest days of his life?

Plz hurry the graph below shows the distances, in miles, that a dragonfly can travel in a certain number of hours: a graph titled motion of a dragonfly shows time in hours on the x axis and distance in miles on the y axis. the scale on the x axis shows number from 0 to 10 at increments of 2 and on the y axis the numbers are shown from 0 to 250 at increments of 50. a straight line joins the ordered pairs 0, 0 and 2, 50 and 4, 100 and 6, 150 based on the graph, what is the dependent variable, the equation relating the two variables, and how far will the dragonfly travel in 24 hours if it continues to fly at the same speed?