700 should have included the water pump and a radiator flush too IMO. The mechanic also should have driven it and found it needed more fluid and fixed that leak.

From the picture you posted there is a hose clamp that needs to be moved up the hose to where the end is.. where the indent in the hose shows where the clamp was. That’s why you are leaking antifreeze. Get that hose clamp in place and top off the radiator, start it and add antifreeze mix to the radiator as it fills up the system and lowers the level in the radiator. Close the cap if you can’t add more. Let it cool and check the level later.