Pronoun Antecedent

I bought the new Lenovo ThinkPad. It is very expensive, but it is very durable and has a great performance. Which is the antecedent for "it" in the previous sentence?

I bought yesterday the DDR4 RAM I needed, but I could not install it in my computer. Which is the antecedent for "it" in the previous sentence?

My sister will come tomorrow. She promised to bring me an i7 14th gen processor, which is my birthday present. Which is the antecedent for "She" in the previous sentence?

Last semester, we took two classes. The first one was programming language and the second one was descriptive geometry. Which the antecedent for "one" in the previous sentence?

Which is the laptop you want purchase? I like the one in silver better. Which is the antecedent for "one" in the previous sentence?

Computer engineering and systems engineering are two technological fields which I was interested in. Both require to develop good computer skills. Which is the antecedent for "Both" in the previous sentence?

In the most general language about computers we will always talk about hardware and software, where the former refers to the actual physical parts that we can see and touch, while the latter refers to the programs or applications. Which is the antecedent for "the latter" in the previous sentence?

We have some students who don’t enter the class, and a result, they will flunk. Which is the antecedent for "they" in the previous sentence?