John chartered a large ship from Rent-a-Boat Ltd. The duration of the charter was 24 months, and it was a term of the contract that Rent-a-Boat would provide a seaworthy ship and supply John with competent engine-room staff. Immediately, there were problems. For example, due to the ship’s engine being old and its engine-room staff being inexperienced, the ship was in repair for the first 20 weeks of the charter. In week 18, John advised Rent-a-Boat that its breaches of contract permitted him to end the contract and sue for damages. Is John correct? What remedy is John entitled to and why?