UJI 13-840. Impossibility or impracticability of performance.

When the performance of a contract obligation becomes impossible or unreasonably burdensome because of circumstances or events beyond the __________________ (promisor’s) control which are substantially and materially different from what both __________________ (plaintiff) and __________________ (defendant) reasonably anticipated would exist, then the __________________ (promisor) is excused from performing that contractual obligation.