cant calculate totalprice

cant calculate totalprice

  
I do it step by step follow sample. But i find it cant work well. in orderdetail , cant calculate totalprice.
hi Hon,

check my solution.

Kings Regards,
Luís Pereira
hi  Luis Pereira
  
 Thank you for your answer.
It work well.
Can you tell me where is wrong in my file.

Thank you.