Note. The results of the entire exercise should be sent in one file with the extension .el as an attachment to an email.

Ex. 1 Write a Lisp program and do the following:

• Declare at least 3 variables, one of which should contain a description.
• Assign numerical values to the three variables.
• Show an example (as many expressions as you want) of using the following mathematical functions, involving the variables you declared: expt, random, abs, cos, truncate.
• Invoke the help on one of the functions listed above and copy it into the program, then comment it out. Hint: when editing a file with the extension .el, a menu option called Emacs-Lisp should appear. You can select the entire region you want to comment out and then use a command in this menu to comment it out.
• Turn the interactive mode on and evaluate your expressions to make sure they are correct.

Ex. 2 Implement the following functions in the same file, complete with short descriptions:

• A function list-sum that returns the sum of the elements of a list, assuming that they are all numbers.
• A function is-in-list that takes two parameters, the first being a list and the second a value, and returns true (t) if the value is in the list and false (nil) if not. Use the function equal to test for equality of two values.