essai

12 items whose price is 5 $ each
12*5C+

15 items whose price is 6 $, on which we perform a discount of 10% 
15*6-10%C+

We perform an overall discount of 15%
*15%C+±

At last, we add a tax of 18%
*18%C+T

Insert a row with 2 items whose price is 4 $ each
2*4C+

Modify a row
.5C+

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