H1B RFE : Do not have a SOW, but can get a Client Letter

My petition has come back for a RFE. The immigration team of my MNC Software company are not ready to share the complete details. They have requested for a SOW. MSA was initially submitted in April. My project does not have a SOW but the client is willing to give me a Client Letter. Will this suffice?

Client letter is ultimate. If you have that you don’t need anything else.