I want to know the answer to the following question:
When were the 18th and 19th satellites for the BeiDou system launched?
All the background I'm provided with is that "On July 25, 2015, the 18th and 19th satellites were successfully launched from the Xichang Satellite Launch Center, marking the first time for China to launch two satellites at once on top of a Long March 3B/Expedition-1 carrier rocket.". Is that enough to answer the question?