For the image below, which values for the charges on the two pith balls could be correct? q1 = +3.7 × 10−6 C; q2 = +3.7 × 10−6 C
q1 = −4.0 × 10−6 C; q2 = +3.5 × 10−6 C
q1 = −4.0 × 10−6 C; q2 = −3.5× 10−6 C
q1 = +3.7 × 10−6 C; q2 = 0.0 × 10−6 C

Determine the change in width a, height b, thickness t when a plate is subjected to the uniform distributed load and is made of material having modulus of elasticity e=230 gpa and poisson's ratio ν=1/3. given : a=400 mm and b= 300 mm also the uniformly distributed load in downward y direction of plate is 2 mn/m and in the positive x direction is 3 mn/m and t=20 mm