A current of 0.76 A flows through a copper wire 0.68 mm in diameter when connected to a potential difference of 15 V. What is the resistivity of copper?
a) 1.75 x 10⁻⁸ Ωm
b) 2.50 x 10⁻⁸ Ωm
c) 3.60 x 10⁻⁸ Ωm
d) 4.90 x 10⁻⁸ Ωm