Answer:
34 kg is the answer to the question
The resistance of an ohmic material is given by

where l is the length and a is the cross sectional area. For a circular wire, this area is that of a circle:

Then solving for diameter, d:

The total is 21. If you use a calculator or count with your fingers it can help make the answer easier so in the end you will get 21 as your total.
When you climb, earth exerts gravitational force on pack in downward direction(pointing towards the center of earth).
In order to climb, you need to work against work done by gravity on the pack.
Hence work done by you = work done by gravity on pack
= Force x displacement = 70 x 30 = 2100 J.