FR6: 1-D Tetris Let an be the number of ways to cover a 1 x n rectangle with 1 x 1 tiles that are black or white and 1 x 2 tiles that are red, yellow, green or purple. Here are 5 examples of the many possible ways to tile 3 1 X n board when n = 5: n a) Compute an for n = 1, 2, 3. b) Find a recurrence relation for an. Reminder: You must explain your recurrence relation c) What are the base cases necessary to solve this recurrence and what are their values? Note: To get full credit for this part, you must use the minimal number of base cases