Answer: the answer would be four thousand
Explanation: hope this helps
The answer is solid because gas is a chemical and water is a compound
The energy carried by the incident light is

where h is the Planck constant and f is the frequency of the light. The threshold frequency is the frequency that corresponds to the minimum energy needed to eject the electrons from the metal, so if we substitute the threshold frequency in the formula, we get the minimum energy the light must have to eject the electrons:
It's being planned to launch in the 2020's