I will assume "Co-bank" is referring to an affiliate. If so I believe this would be covered under Reg. W 223.11. You may want to look to Section E to see if it falls within an exemption. I haven't dealt with affiliate banks for over 10 years so I'm not as up on this specific Reg. as I probably should be.
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The opinions expressed are mine and they are not to be taken as legal advice.