Physics P3 help

[Adorkableme]

guys plz help with part (b) of this question its confusing me.
I attached the question.

 

[unplugged]

a) i) R = 1.8/0.45 = 4 ohm
ii) Energy released every second = 4 x 0.45^2 = 0.81j
Energy released in 9 minutes = 0.81 x 60 x 9 = 437J
b) 4 x A/L = 6 x 1/4A / L2
4/l = 1.5/L2
4L2 = 1.5L
L2 = 3/8 L