Math gurus please help. How do I cut my fabric?

[goofyizzy]

I have finally decided on a pattern for a quilt for my own bed. I've been quilting for the years now. It's about time. I want the quilt to be made from one block. I have figured out what size pieces to cut to make the block finish at 10" square. I have 20 fat quarters each measuring about 18"x 21".

Can someone help me figure out how to cut each fat quarter to get the most yield? How many blocks can I make? I have a king size bed. I think I need at least 90 blocks. I will add some length and width with a wide border. I have an extra yard and half of a one of the prints that can be incorporated into the blocks if needed. I won't be using the fat quarters for the background (snowballs).

Each block requires
4 - 4 1/2" squares for the main fabric
4 - 2 1/2" squares for the contrast squares
1 - 6 1/2" rectangle for the plus sign
2- 2 1/2" squares for the plus sign

and 8 - 2 1/2 " squares from background fabric for the snowballs. Bonus points if you can tell me how much fabric I need for snowballs for 90 blocks and to border the quilt to make big enough for a king size quilt.

Here's a picture of my test block. These are not the fabrics I will be using.