How to find the range of a data set?

Ineed someone to me answer my question i have to have this done and knocked out

The graph shows the amount of total rainfall at each hour what was the total rainfall amount after three hours

6. sarah saved $12.75 every week for a number of weeks, w. she received an additional $25 during the last week in which she saved money. write and solve an equation to find the number of weeks, w, for which sarah had saved money if she has $114.25 now.