MANILA, Philippines — The Metropolitan Manila Development Authority (MMDA) has extended its free towing service for vehicles that become submerged, stranded or trapped in floodwaters until Friday, Aug. 21.The extension is intended to accommodate more motorists who may need assistance amid flooding brought by rains from the southwest monsoon or Habagat, MMDA said.The MMDA said that the service covers vehicles that entered floodwaters or became st…