**1. The problem statement, all variables and given/known data**

Hey, I have problems solving this question. May I know how to solve this question. Somehow, the answer I got is to the power of negative. can someone show me the step by step solution to this question? (Question 18 from this paper) the link is below.

http://ift.tt/1jwE5MB

**2. Relevant equations**

E = Fl / Ae

**3. The attempt at a solution**

http://ift.tt/1jwE5MD