In the absence of express or implied agreement of the parties, acceptance of the goods by the buyer shall not discharge the seller from liability in damages or other legal remedy for breach of any promise or warranty in the contract of sale. But, if, after acceptance of the goods, the buyer fails to give notice to the seller of the breach in any promise of warranty within a reasonable time after the buyer knows, or ought to know of such breach, the seller shall not be liable therefor. (n)