Solve the given question:
Question: Romeo takes a uniform 12 m ladder and leans it against the smooth wall of the Capulet residence. The ladder's mass is 19.0 kg, and the bottom rests on the ground 2.8 m from the wall. When Romeo, whose mass is 73 kg, gets 90% of the way to the top, the ladder begins to slip.
Part A- What is the coefficient of static friction between the ground and the ladder?
Show all work, use additional paper if necessary.