(b) (i) A thin spherical shell of radius R has a uniform surface charge density $\sigma$. Using Gauss' law, deduce an expression for electric field (i) outside and (ii) inside the shell. (ii) Two long straight thin wires AB and CD have linear charge densities $10 \text{ } \mu\text{C/m}$ and $-20 \text{ } \mu\text{C/m}$, respectively. They are kept parallel to each other at a distance $1 \text{ m}$. Find magnitude and direction of the net electric field at a point midway between them.