Affidavit of Support of I485 RFE

[caiyw]

Part of my I485 asked for "affidavit of support for my family", anybody has experience answering this FRE, particularly:

1) Do I need to file form I-134, or a simple letter stating my support for the family is enough?

2) Is the I-134 what I need to file, or I have to file some other forms?

Thanks,

caiyw001