Calculating Resistance for Cylindrical Conductors

[delsoo]

Homework Statement

can anybody help me with this question? my ans is different from the ans given... i need explanation on this ! here's my attempt by the way.
r=pl/a . r=resistance , p = resistivity l=length

r=(1.69e-8)(2pi )(6e-2 +1.5 e-3 )(300) / (pi )(1.5e-3)^2

what's wrong with my working? p/s e =1 x 10^x

Homework Equations

The Attempt at a Solution

 

[mfb]

You ignored the perfect electrical contact between successive turns. You don't have a single long wire, you have a conducting cylinder.

(6e-2 +1.5 e-3 )

Minor detail: this is the outer radius, not the average radius.