How to sum formulated and assigned texts as below:

[sameer786af]

Company A	a+2*b+3*c		a=product X
company B	5*b+2*c		b=product Y
Company C	4*a+6*c		c=product Z

Total Product X = 

Total Product Y=

Total Product Z= 

Total for all products = 

Thank you for your help.