First of all, hello to everyone here.

Can anyone help me with the following structural mechanics problem.

I have attached a word document showing the working out of a problem. My issue is that I cannot see that these answers can be right. Clearly -80,000K is impossible, and the answer for the second one seems way off the mark too.

I feel there must be something wrong with my transposition of the formula, but I can't seem to find the problem.