12. A 3.0-m-long uniform ladder with a mass of 12 kg leans against a frictionless wall. The ladder Is inclined at an angle of 70" above the floor. The coefficient of static friction between the ladder and the floor is 0.28. A person has left a 25-kg toolbox on a rung 75% of the way up the ladder. a. Calculate the force of static friction acting at the bottom of the ladder for the system as shown. b. Will the ladder start to slide? Justify your answer numerically. C. How high up the ladder could the box be placed before the ladder starts sliding