This is forces unit please use forces formulas (F=ma)(f=mg)(Ff=uF) and the rest of force formulas or big 5 equations. include force body digram

4. Draw a free-body diagram to determine the net force acting on the object in italics in each of the following situations: [ (a) Two teenagers are pushing a dirt bike through a freshly plowed field. One exerts a force of 390 N [W] on the bike while the other exerts a force of 430 N [W]. Frictional resistance amounts to 810 N. (b) A water-skier is being pulled directly behind a motorboat at a constant speed of 20.0 m/s. The tension in the horizontal rope is 520 N. (c) An elevator, including passengers, has a mass of 1.0 x 103 kg. The cable attached to the elevator exerts an upward force of 1.2 x 104 N. Friction opposing the motion of the elevator is 1.5 x 103 N