On June $1,2015,$ by signed writing, JelCorp and NetCorp form a contract that bears these terms:

Item $1$: JelCorp hereby promises to buy from NetCorp, for the price of $$450,000,$ NetCorp's Hubdie machine, delivery to be made by NetCorp to JelCorp at JelCorp's main processing center on September $9,2015,$ except that JelCorp need not make the purchase if$,$ before August $1,2019,$ the U$.$S Congress repeals the presently effective accelerated depreciation statute applicable to the purchase of a Hubdie machine.

Item $2$: NetCorp promises, in accordance with item $1$ above, to deliver the Hubdie machine to JelCorp.

On July $1,2019,$ the U$.$S$.$ Congress repeals the accelerated depreciation statute applicable to the purchase of a Hubdie machine.

JelCorp contacts NetCorp: $"$As you may know, Congress has repealed the accelerated depreciation statute. We are not willing to purchase. Please do not deliver." NetCorp responds, $"$We don't insist on the condition that concerns the depreciation statute. We're ready to proceed and expect you to purchase." If JelCorp refuses to pay for the machine, does it breach its contract with NetCorp?