P1 a4 learning types

A city library is planning three systems. Identify the type of machine learning (supervised, unsupervised or reinforcement) that each one uses.

(a) A model is trained on 5000 past book reviews, each already tagged by staff as positive or negative. It then tags new reviews. [1]

(b) A model sorts library members into groups with similar borrowing habits. Nobody tells it what the groups should be. [1]

(c) A program controls a book-sorting robot arm. It gains a point for each book placed on the right shelf and loses a point for each book dropped, and it improves its movements over thousands of attempts. [1]

[3]