a) In your fridge you have ham, roast beef, turkey, brown and white bread, mayonnaise, and mustard. You are allowed to make a sandwich with 1 type of meat, 1 type of bread, and 1 condiment. Using a tree diagram, determine how many different sandwiches can be made.

b) Using the placeholder method, determine how many even 4-digit numbers can be made using the digits {0, 2, 5, 6, 8, 9}.

c) If 11 people are lined up and Ralf must be first, and Sonja, Sandra, and Kent must be together, explain in words why the number of permutations is 241 920

d) Using permutations, determine how many ways a president, a vice-president, and a secretary can be picked from a group of 15.