Two wires P and Q are made of the same metallic material and maintained at the same temperature. Wire P has length L and diameter d, while wire Q has length 1.5 L and diameter 0.8 d.
(i) Using appropriate reasoning, obtain the ratio of their resistances RP:RQ.
(ii) If the resistance of wire Q is 6 Ω, calculate the resistance of wire P.
(iii) The two wires are now connected in series to a battery. Find the effective resistance of the series combination.