Need help with probability question

Problem 1 1) A lottery manager selects a winning number based on the following rule. The winning number comprises of 4 digits which are selected at random from the set {0, 1, 2, 3, 4, 5, 6, 7, 8, 9} . It is permissible for a digit to be selected any number of times. How many ways can the lottery manager select the winning number? 2) In an exam manual, there are 15 questions in total. Out of the 15 questions, 6 are theoretical and 9 are practical. Suppose that an examiner wants to prepare exam problem sets based on the manual. Each problem set consists of 2 theoretical and 4 practical questions. How many different problem sets can the examiner prepare? 3) In a Communication class of 10 students, a professor plans to pick 2 students to work on Project A, 3 to work on Project B, and 5 to work on Project C. How many different ways can the professor assign students to projects