A student's work on the following problem is shown. light in the ocean will decrease with depth. the average depth for light is 600 meters, with a variance of 400 meters. write and solve an absolute value equation to represent the depth.

In the student's work on the problem, where did they make their first mistake?

a) Step One: |d - 600| = 400

b) Step Two: d - 600 = 400, d + 600 = 400

c) Step Three: 600 - 600, 600 + 600, 600 - 600, 600 + 600

d) Step Four: d = 1,000, d = 200