FIRST find the VOLUME of the wire:
pi x r^2 x l = 5.45 x10^-7 m^3
THEN find its diameter given the NEW length of 1.5028 M
pi x r^2 x l = 5.45 x 10^-7 results in r =3.3968 x10^-4 m
then, as before Stress = F/A F= ma = 6.8(9.8) = 66.64 newtons
A= area = pi x r^2 where r is the 'new ' stretched r
Let me know what you come up with for an answer and we will continue..... ~EP