Two box$-$shaped resistors with square end caps are made from the same material are shown, with their relative dimensions, above $($the perfectly conducting leads are the vertical whiskers$).$

$($a$)(10$ points$)$ What is the ratio $R\frac{a}{R}B?$

$($b$)(10$ points$)$ What are Ra and Re if $L=10cm,$ resistivity is $2{10}^{-1}$ohmM $?$

$($c$)(10$ points$)$ We will use Ra and two Rb resistors in the circuit below.

Determine total resistance of the circuit that uses $20$ V battery.