(b)an implied condition that the goods shall be of merchantable quality, but no such condition shall be implied by virtue of this clause(i)as regards defects of which the owner could not reasonably have been aware at the time when the agreement was made, or(ii)as regards defects specified in the agreement (whether referred to in the agreement as defects or by any other description to the like effect), or(iii)where the hirer has examined the goods, or a sample thereof, as regards defects which the examination ought to have revealed, or(iv)if the goods are second-hand goods and the agreement contains a statement to that effect.