Aforce of magnitude f1 is applied to pull the block up the incline at constant speed. the coefficient of kinetic friction between the plane and the block is μ.

1. what is the total work wfric done on the block by the force of friction as the block moves a distance l up the incline? express the work done by friction in terms of any or all of the variables μ, m, g, θ, l, and f1.
2. what is the total work wf1 done on the block by the applied force f⃗ 1 as the block moves a distance l up the incline? express your answer in terms of any or all of the variables μ, m, g, θ, l, and f1.