5. Below are five computational tasks. For each one, choose the data structure or abstract data type you feel best suited to the task from the following list: Stack, Queue, Hashtable, AVL Tree, Priority Queue, Union-Find. In addition, list the basic operations for the data structure or ADT that you chose and give asymptotic worst-case running times for those operations. No additional explanation is required.

(a) While processing a list of objects, check if you have processed a particular object before.

(b) Store a list of students and their grades. You must also provide an efficient way for a client to see all students sorted in alphabetical order by name. Give the running time for this operation as well.

(c) Process a digital image to divide the image up into groups of pixels of the same color.

(d) Compute a frequency analysis on a file. That is, count the number of times each character occurs in the file, and store the results.

(e) Store the activation records (i.e. objects containing the return address and local variable associated with a function call) for nested function calls.