Answer: The contract was in place on 23rd April.
Explanation: In my opinion, the contract was in place on 23rd April. You revert to them on 16th April. But the vendor received the letter on 23rd April. It is called a contract only when both parties have a written agreement and it has to be intended to be enforceable by law. so it is on 23rd April, that both parties acknowledged it and received it.