how to concatenate 6 fields in one multiline field

Question

In my infopath , there are 6 fields (TextField):

1. A

2. B

3. C

4. D

5. E

6. F

wanted to merge all fields values and display it in 7. G (multiline) field.

so i create a multiline field (G) and wrote infopath rule field (G):

Rule Type:Action

Run these action: Set a field's value

Field: select G field

Value: Concat(A,B,C,D,E,F)

but still rule is not working and value is not displaying in Field G.