A0.600-mm diameter wire stretches 0.500% of its length when it is stretched with a tension of 20.0 n. what is the young's modulus of this wire?

The Young modulus is given by:

where
F is the force applied
is the initial length of the wire
is the cross-sectional area of the wire
is the stretch of the wire

The wire in the problem stretches by  of its length, this means 


We can also calculate the area of the wire; its radius is in fact half the diameter:

and so the area is


We know the force applied to the wire, F=20 N, so now we have everything to calculate the Young modulus:

Edit the post so i can see the letters for each answer, and increase the points required so i'd be able to answer it.