The drawing shows a large cube (mass = 35 kg) being accelerated across a horizontal frictionless surface by a horizontal force P. A small cube (mass = 2.2 kg) is in contact with the front surface of the large cube and will slide downward unless P is sufficiently large. The coefficient of static friction between the cubes is 0.71. What is the smallest magnitude that P can have in order to keep the small cube from sliding downward?