Exercises 2.4.20 was graded out of three points, and exercises 2.2.12, 2.2.34, 2.3.18 out of two points. The last point was given for free for handing in a homework.
In 2.2.34, A lot of students just wrote that the answer was minus infinity, without any justification. In the future, I will not give any credit for this: any answers in any work you hand out anywhere should be justified.
Also, I do not recommend the "calculator" method to compute limits, as there are times when it does not work, and also because it does not give much insight. In any case, just citing values computed with a calculator is usually not enough justification for why the value of a limit is what it is. Computing points with a calculator could still be used to get a first guess, if really you have no idea.