A line graph is shown where x-axis is 'Millions of Years' ranges from 0 to 700 with an increment of 100 and y-axis is 'Relative Mass of Discovered Rocks' ranges from minus 0 to 7 with an increment of 1. A line passes through points (200 comma 6.3), (400 comma 3.8) and (600 comma 2.2). The third point is marked as Oldest animal fossils.