[solved] "Change value of single field" acttion - error - remember Constants are "text"

0

Error:
[Quote]
Error occured during business rule evaluation.

String values cannot be multiplied
at: Evaluation requested
at: Evaluation node: Operator (+)
at: Evaluation node: Operator (*)
at: Evaluation node: Operator (*)
[/Quote]

What I have :
-process static A
-process static B
-process static C
-process static D

attribte a,b,c
attribute a,b,c is changing dynamically vs Item List

attribte d

I try to change Value of Attribute D on path .. = error OK, then is not saved data so I move step forward .. but again error ...

so .. how to calculate:
D = (A*B)*a + (A*B)*b+(A*C)*c ?

why I don't have rulle in a,b,c to "fix" D" ? .. I did not JS and ten I had error multiple time run rule ... so next idea was change in transaction on path