Minerals Ltd. contracts to provide several manufacturers with tin. When a cartel of tin-producing countries suddenly embargoes future shipments of tin to Minerals so that it cannot fulfill its contracts, the distributor​
a. ​can substitute some other material for the tin.
b. ​is excused from the performance of its contracts.
c. ​is liable for breach of contract.
d. ​must still supply the tin needs of its customers.