Stahl Corp. entered into a written contract to purchase a warehouse from Mehl for $$385,000.$ Thereafter, Mehl received an offer from another purchaser to buy the warehouse for $$395,000.$ As a result, Mehl has refused to transfer the warehouse to Stahl. Stahl has commenced an action for specific performance. Mehl has raised the statute of frauds as a defense. In order for Stahl to successfully prevail on the statute of frauds issue, it must be shown among other requirements that the contract was signed by:

a$.$ Stahl.

b$.$ Stahl and Mehl with proper notarizations affixed to the contract.

c$.$ Mehl.

d$.$ Stahl and Mehl at the same time.