Quantifying the worse case scenario

[Guest Greetad]

Client is acquiring Company A in a stock deal. Company A has recently disclosed a serious operational error and Form 5500 filling mistakes for their Retirement Plan. Assume for our purposes that Client has no option other than assuming liability for the shoddy Plan. In order to negotiate a hold-back amount for the transaction, Client has asked us to quantify the Worse Case Scenario if the Service were to disqualify the Plan. (The Service is currently auditing Client and therefore, Audit CAP is the only available correction program if this matters.) Retirement Plan as about 160 participants and $5.5M in assets.

Any idea how I would begin to quantify?

Thanks in advance.