I have the m1=1139, v10=1.984,and vf=1022 but I need to find m2 and I don't know how I'm supposed to do that. The equation m1*v10=(m1+m2)*vf. Please help as soon as you can.

Ahuge (essentially infinite) horizontal nonconducting sheet 10.0 cm thick has charge uniformly spread over both faces. the upper face carries +95.0 nc/m2 while the lower face carries -25.0 nc/ m2. what is the magnitude of the electric field at a point within the sheet 2.00 cm below the upper face? (ε0 = 8.85 × 10-12 c2/n · m2)