Please answer 3a-b and number 4 as well please. With explanation

3. A laboratory balance essentially uses the method of moments to compare an unknown mass with a known mass. Some balances have constant and equal lever arms, and others do not. Fig. 4(a) shows the balance used in our lab. Its sketch diagram is shown in Fig. 4(b), where m, is the unknown mass, m2 is the known mass and me is the mass of the metal scale bar. pivot point m m (b) (a) Figure 4 A laboratory balance (a) and its sketch diagram (b) (a) Explain how the condition _ F =0 is satisfied for the balance in Fig. 4 (b). (b) Explain how the condition [ =0 is satisfied for the balance in Fig. 4 (b). The torques are calculated about the rotating axis through the pivot point O. Does the individual torque depend on the position of the rotating axis? Does the second equilibrium condition ( _ 7 = 0) of a rigid body depend on the position of the rotating axis? Why