A 3.0 kg block is acted upon by a horizontal force f(x) = 26.0 - 9.0x where the force is measured in newtons if x is measured in meters. the coefficient of kinetic friction between the block and the flat surface is 0.20. the block is initially at x = 0 m. what distance must the block travel if the net work done on the block by f(x) and friction combined is to be exactly zero?