1. Define the following recursive Logo procedure:

   to countdown :number
    print :number
    countdown :number-1
    if equalp :number 0 [stop]
   end
   

   This procedure is supposed to look like this when run:

   ? countdown 5
   5
   4
   3
   2
   1
   0
   ?
   

   Try it -- it doesn't work! Use the Logo menu to stop the procedure.

   Why doesn't the procedure work?

2. Edit the countdown procedure so that it works as intended.

3. Write a recursive procedure sumup that takes a positive integer n as input and outputs the sum 1 + 2 + 3 + ... + n. You may find it helpful to review the initials.recursive procedure from Lecture 13.

Bonus (5 pts) Write a recursive procedure triangleview that draws a collection of nested triangles similar to those shown below.