thank you, i got the right values now for 13.2a,b,c. However i went to do the P&L and my answer isn't correct. How do I calculate the PBT ? I did sales =3.550.000*0,4+218000*13 = 4252000. I believe here is my problem : for the COGS I did 3550000(units sold)*0,2556(COGM/UNIT)+218000*8,6689 = 2797200,2. This way I get a gross profit of 1456799,8. I take out non man cost of 347800, which gives me 1.108.799,8 and not 1 134 668.33. Where did I go wrong ? what do I do to fix it ?