A graph, plotting a the relationship between a bond’s modified duration and its tenor for a

1. A graph, plotting a the relationship between a bond’s modified duration and its tenor for a (10) zero, (10) discount bond, (10) premium bond and (10) perpetuity
2. In (10 per) writing, and by (5 per) showing numerical analysis, explain what drives the shape of the four curves you plotted in part 1