Derive the expression for electrical conductivity of a material in terms of relaxation time

Dear Student,
Expression for Conductance:

The relation for drift velocity is given by 
$V_d$=eET/m
And the current through the conductor will be,

I = neA$V_d$ = n $e^2$A(ET/m)             {$e$=charge of electron,A=cross sectional area,T=relaxation time,$V_d$=drift velocity of electron}
As, the electric field E is equal to V/L

So,

I = n$e^2$A(VT/Lm)                             {L=length of conducting wire}

I/V = n$e^2$​​​​​​A(T/Lm)
R = Lm/ n$e^2$AT
Since, Resistivity = R A/L,
Replacing 'R' in Resistivity's expression:
Resistivity = (Lm/ n$e^2$AT)(A/L)
Resistivity = m/n$e^2$T
Conductivity = n$e^2$(T/m)
Thanks,
Regards