Exercises 3.2.50,3.4.84 were both graded out of 3 points (one point for (a), two points for (b)). Exercise 3.4.72 was also graded out of three points, with one point for the correct value for f', and two for the correct value of f''. The last point was given for free to anyone who handed out something.
In 3.4.72, remember to use the chain rule: the derivative of g(x2) is g'(x2)2x (some of you forgot this 2x: the derivative of the inner function). In 3.4.84, remember to justify why the limit in (a) is 1.