Final answer:
Bob should attach the horizontal support bar about 110.5 inches from the top along the legs.
Step-by-step explanation:
To determine how far from the top along the legs Bob should attach the horizontal support bar, we can use the Pythagorean theorem. The distance between the legs on the ground forms the base of a right triangle, with the length of each leg as the other two sides. We can calculate the height of the triangle using the Pythagorean theorem: h^2 = leg^2 - (distance/2)^2. Plugging in the values given, we have h^2 = 120^2 - (82/2)^2. Solving for h, we find h ≈ 110.5 inches. Therefore, Bob should attach the horizontal support bar about 110.5 inches from the top along the legs.