Visa Information Request (Mulitple city visit)

Good morning,
We (Belgian citizens) would like to visit China with a tourist visa (15 days)
Purpose is to visit aswell Beijing Shanghai Hong Kong (Total tour arranged by travel agency)
do we need a single entry visa or a multiple entry for this trip ?
As I can see on the website total cost for a Single Entry is 50€ 36,3 € . Correct ?

We still need to book our trip to China, so we do not have the flight and hotel details yet !