Need Help To Develop A Formula For Multi-Level Selling!

Assume u recruit 8 sales 1st year, 2 left the next year and 4 promoted
to become a manager in the third yr.  When the 4 become manager, they
will repeat the recruitment process everyyear while u keep on recruit
sales everyyear.

Let the production of every sales in the 1st year is $120,000 and
$180,000 for the rest of life.

Also, the commission for u is scale up everyyear for example is 8%,
17%, 28%, 39%, 52%, 68% on the production and your subordinates will
enjoy the same scale of commission after promoted.  In addition,u can
enjoy the production  of your subordinate's subordinates by the
different of level of commission.
For example, when u earn 28% at the 3rd year, your immediate
subordinate earn 8% then u will enjoy his subordinates production at a
rate of 20% (i.e. 28%-8%).

Moreover, the commission rate is constant for old sales and new
commission rate is only apply to new sales. For example, the 8 sales u
recruit at 1st year, u can enjoy 8% commission on their production for
the rest of their life/ production.  When u promote next year, the 
17% commission rate only apply to the new recruited sales rather than
the old one/ sales.

Under such condition, I would like to know how much I earn at the end
of 7th year.

Million Thanks!!