a copper conductor 1km long has a resistance of 4.3ohms. calculate the cross sectional area of the conductor?

Question

The resistivity of copper is 17.24 nanohm meters.
can some one show me all the workings of this question including the formula used.

Answer 1

R = ρL/A
A = ρL/R
A = (17.24*10^-9 Ω•m)(1,000 m)/4.2Ω
A = 4.104762*10^-6 m^2 ≈ 4.1 mm^2

Answer 2

from the general formula

R=resistivityXlength over its cross sec. area

R= p L/A

R= 4.3 ohms
p= 17.24 X10^-9 ohms
A= unknown
subs. values
A=4.0093023X^10 -6 m^2
or 4sqmm