Lehman is fighting the IRS, and uses the services of Morgan, a CPA. The day before Lehman must file a response to the IRS, Morgan says she will not give him the final calculations unless he pays her double what she had agreed to before. Lehman pays, but later sues. A court might find that the agreement was unenforceable because of:

A court might find that the agreement was unenforceable because of economic duress.

Explanation:

Economic duress is considered as an argument to make unenforceable an agreement when a party threatens to cancel the ongoing contract.

The most important part of the argument is that Lehman paid but later sued. A key element of economic duress argument is that the party that accepted the new terms under duress had no other choice available to them.

If Lehman demonstrates that they entered into the contract without other alternatives, they can take Morgan to court.