All bridges built from 1950 to 1960 are in serious need of rehabilitation. Some bridges constructed in this period, however, were built according to faulty engineering design. That is the bad news. The good news is that at least some bridges in serious need of rehabilitation are not suspension bridges, since no suspension bridges are among the bridges that were built according to faulty engineering design.
Some bridges built from 1950 to 1960 are not in serious need of rehabilitation must also be true if the statements above are true, on the basis of those statements.