A conductor with rectangular cross-section has dimensions \( (a \times 2 a \times 4 a) \) as sho...

A conductor with rectangular cross-section has dimensions \( (a \times 2 a \times 4 a) \) as shown in figure. Resistance across \( A B \) is \( R_{1} \), across \( C D \) is \( R_{2} \) and across \( E F \) is \( R_{3} \). Then,
(a) \( R_{1}=R_{2}=R_{3} \)
(b) \( R_{1}R_{2}R_{3} \)
(c) \( R_{2}R_{3}R_{1} \)
(d) \( R_{1}R_{3}R_{2} \)