Using the law of conservation of energy, we know that energy can neither be created nor destroyed but can only be transformed from one state to another. Therefore, the kinetic energy at the inclined bottom equals to the potential energy at the top hence
and making v the subject of the formula then where m represnt the mass of sled, v is the initial speed, g is acceleration due to gravity and h ia the vertical height. Substituting g with 9.81 m/s2 and h with 1.22 then
I assume that the force of 20 N is applied along the direction of motion and was applied for the whole 6 meters, the formula of work is this; Work = force * distance * cosθ where θ is zero degrees. Plugging in the data to the formula; Work = 20 N * 6 m * cos 0º.