In this set of exercises, you will build up images of ice cream cones.
The teachpack provides an image of an empty ice-cream cone (called
empty-cone).  Scoops of ice cream can be drawn as circles.  Using the
overlay/xy operation on images, you can add new scoops to the top of
existing cones.

1. Write a function scoop-image that consumes a symbol (a color) and
produces an image of a scoop of ice cream in that color.  (A circle of
radius 25 works well with the cone size -- write a constant for the
scoop size.)
 
2. Write a function add-chips that consumes the image of a scoop of
ice cream and produces an image of the scoop with chocolate chips
added.  (Use small rectangles for the chips.)

3. Write a function create-scoop that consumes a symbol (a color) and
a boolean indicating whether or not the scoop should have chips and
produces an appropriate image of the scoop (depending on the boolean).

4. Write a function add-scoop that consumes an image of a scoop and an
image of a cone (with or without ice cream already on it) and produces
an image of the cone with the new scoop added to the top.  [hint: you
may need to use center-pinhole (from the teachpack) to put the pinhole
of the cone image in the right place.]

5. Real ice cream scoops are lumpier than plain circles. We can make
our scoops look lumpy by adding a small circle of the same color
hanging off the lower edge of each scoop (and over the scoop or cone
underneath).  Write a function add-fancy-scoop that takes a scoop color
and a cone image (with or without ice cream already on it) and
produces an image of the cone with a lumpy scoop of that color on top.

6. Write a function add-fancy-chip-scoop that has the same contract as
add-fancy-scoop, but also adds chips to the new scoop.

7. Write a function cone-price that consumes a cone image and produces
the price of the cone.  An empty cone costs $1 and each additional
scoop costs 75 cents (the chips are free).  Use the height of the
empty cone and scoop images to figure out the price.

Bon appetit!