A rod with original length 80 mm experiences a length change to 20 mm. Calculate the strain.

Let's break down this problem step by step, using the information provided and making reasonable assumptions based on typical physics problems involving rods. We will assume the rod mentioned here is the same one from the previous problem, with a diameter of $80 \text{ mm}$.

a) Strain
Strain ($\epsilon$) is defined as the change in length ($\Delta L$) divided by the original length ($L_0$). From your written work, it appears you are using $\Delta L = (20 - 28)$ and $L_0 = 80$.

Step 1: Calculate the change in length ($\Delta L$).

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