â–« Proposal not containing the required elements, exhibits, nor organized in the required format. To participate in the RFQ process, you must be fully registered with iSupplier.Here is information on Selling to the City of Oakland. A Proposer's proposal is an irrevocable offer for ninety (90) days following the proposal due date. Interested firms are invited to submit a proposal that responds to the Scope of Services described herein. The proposal must comply with the.