1. Which of the following sets can be described in complete listing, partial listing and/or setbuilder methods? Describe each set by at least one of the three methods. a) The set of the first 10 letters in the English alphabet. b) The set of all countries in the world. c) The set of students of Addis Ababa University in the 2018/2019 academic year. d) The set of positive multiples of 5 . e) The set of all horses with six legs.

Let's describe each of the sets using complete listing, partial listing, and/or set-builder notation as appropriate. ### a) The set of the first 10 letters in the English alphabet. - **Complete Listing**: {A, B, C, D, E, F, G, H, I, J} - **Set-Builder Notation**: {x | x is a letter in the English alphabet and 1 ≤ position of x ≤ 10} ### b) The set of all countries in the world. - **Partial Listing**: {United States, Canada, Brazil, Germany, China, India, Australia, South Africa, Japan, France, ...} (and so on) - **Set-Builder Notation**: {x | x is a country recognized by the United Nations} ### c) The set of students of Addis Ababa University in the 2018/2019 academic year. - **Partial Listing**: {Student1, Student2, Student3, ..., StudentN} (where Student1, Student2, etc., represent actual student names) - **Set-Builder Notation**: {x | x is a student enrolled at Addis Ababa University during the 2018/2019 academic year} ### d) The set of positive multiples of 5. - **Set-Builder Notation**: {x | x = 5n, n ∈ ℕ} (where ℕ is the set of natural numbers) - **Complete Listing**: {5, 10, 15, 20, 25, 30, ...} (this can continue indefinitely) ### e) The set of all horses with six legs. - **Set-Builder Notation**: {x | x is a horse and x has 6 legs} - **Description**: This set is likely empty, as there are no known horses with six legs. Thus, it can also be described as the empty set: ∅. In summary, each set can be described using different methods, with some sets being more suitable for certain methods than others.