Part 1. When x=0, then y=900 (from the graph). This means that y-intercept is at point (0,900).
Answer Part 1: 900
Part 2. The y-intercept is at point (0,900). This means that at x=0 (loads), the total amount of dirt to remove is 900 cubic feet.
Answer Part 2: the total amount of dirt to remove.