Shana is hiking down into a canyon. The table shows her elevation above the canyon floor at different hours during the course of the hike. A linear function represents the relationship between the number of hours Shana has hiked and her elevation.
Number of hours Elevation (in feet)
1 3,500
3 2,100
4.5 1,050
5 700
What is the initial value of the function? Explaln how you know.