Two rectangular blocks are stacked on a table. The lower block has a mass of 38.6 kg and upper block has a mass of 3.40 kg. The coefficient of kinetic friction among the lower block and the table is 0.260. The coefficient of static friction among the blocks is 0.551. A string is attached to the lower block and an external force −"F is applied horizontally, pulling on the string. (a) What is the maximum force that can be applied to the string without having the upper block slide off? (b) If a force of magnitude 500N is applied, at what angle above the horizontal should it be directed in order for the upper block to remain stationary by respect to the lower block?