Starting from rest, a horse pulls a 263−kg cart for a distance of 1.6 km. it reaches a speed of 0.38 m/s by the time it has walked 50.0 m and then walks at constant speed. the frictional force on the rolling cart is a constant 253 n. each gram of oats the horse eats releases 9 kj of energy; 10 % of this energy can go into the work the horse must do to pull the cart. how many grams of oats must the horse eat to pull the cart?