A copper rod of 88 cm and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of aluminium rod is : (αCu = 1.7 × 10–5 K–1 and αAl = 2.2 × 10–5 K–1)
(1) 6.8 cm
(2) 113.9 cm
(3) 88 cm
(4) 68 cm