Answer:
a. Linda's acceptance is effective and a contract is created.
Explanation:
A contract is created when there is an offer and acceptance of a transaction. When the contract is created it is enforceable and not revocable unless with the consent of parties involved.
Bob made an offer to Linda to buy her 1,000 of her widgets. The offer is open for 3 weeks and Linda accepted the offer within one week.
Although Bob tried to revoke the offer, since Linda has accepted it the contract is created and enforceable on Bob.