how would i solve these three problems?

Physics 1351 - Discussion 6 Lou's Bet Lou bets an innocent stranger that he can place a 4.00 kg block against the side of a cart, as in the figure, and that the block will not fall to the ground, even though Lou will use no hooks, ropes, fasteners, magnets, glue, or adhesives of any kind. When the stranger accepts the bet, Lou begins to push the cart in the direction shown. The coefficient of static friction between the block and the cart is 0.700. a) What is the magnitude of the frictional force in the case where Lou wins the bet (and the block sticks to the cart)? b) Find the minimum acceleration for which Lou will win the bet. c) Show that, for a block of any mass, the block will not fall if the acceleration a 2 /us, where us is the coefficient of static friction