------------------------------                                     
|sale 1|number|cost|extension|                                      
------------------------------                                     
|shirts|  3  |     |         |                                     
------------------------------                                     
|  ties|  2  |     |         |                                     
------------------------------                                     
| total|     |     |   69    |                                     
------------------------------                                     
------------------------------                                     
|sale 2|number|cost|extension|                                      
------------------------------                                     
|shirts|  2   |    |         |                                     
------------------------------                                     
|  ties|  4   |    |         |                                     
------------------------------                                     
| total|      |    |   66    |                                     
------------------------------                                     
ratio = sale 2's number of ties / sale 1's number of ties;         
sale 1's shirts's cost =                                           
   (ratio X sale 1's total extension - sale 2's total extension) / 
   (ratio X sale 1's number of shirts - sale 2's number of shirts);
sale 1's ties's cost =                                             
   (sale 1's total extension - sale 1's number of shirts X         
    sale 1's shirts's cost) / sale 1's number of ties;