Where a purchaser orders goods or materials of a type, size or quality not produced by the Company in the ordinary course of its business, the Company will use all reasonable endeavours to execute the order. If it subsequently proves impossible, impracticable or uneconomical to complete the order the Company reserves the right to cancel the contract or the incomplete balance thereof, in which event the purchaser will only be liable to pay for such part of the contract as has been performed, the purchaser will be responsible for costs of materials and labour incurred by cancellations, or design changes, once the order has been accepted.