Comments:

- For Section 2.1 no. 36, remember another formula to derive the derivative of a function, say f(x), at x=a, which is \lim_{t\to a}\frac{f(x)-f(a)}{x-a}.
- Some students forgot to explain the meaning of the graph of P'(t) in Section 2.2 no. 12, or forgot to mention the domains of the function and the derivative in Section 2.2 no. 20.