While a roofer is working on a roof that slants at 44.0 degrees above the horizontal, he accidentally nudges his 88.0 N toolbox, causing it to start sliding downward, starting from rest. If it starts 4.15 m from the lower edge of the roof, how fast will the toolbox be moving just as it reaches the edge of the roof if the kinetic friction force on it is 21.0 N? To get the velocity I must do 2*a*4.15 (and then take the square root of the answer). I think the problem I am having is getting the correct acceleration. I have gotten 5.18 and 2.56. Both have gotten me nowhere. I really don't know what else to do, please help.