Answer:
The volume of water evaporated is 199mL
Explanation:
Concentration is calculated with the following formula

where n is the number of moles of solute and V is the volume of the solution (in this case is the same as the solvent volume) in liters.
So we isolate the variable n to know the amount of moles, using the volume given in liters


Now, we isolate the variable V to know the new volume with the new concentration given.

Finally, the volume of water evaporated is the difference between initial and final volume.

Depends. Are you talking about a mathematical 4th dimension (in which there is infinite dimensions) or some sort of etheral dimension (in which there is no scientific evidence for)
If you mean the first then yes. But it depends how these beings exist. From our understanding we only can theorize shapes in 4-d and if we assume that there is only one universe these "beings" arleady exist and thus any message in 3-d would be sent to them like a shadow ("flat").
If they exist in a alternate "plane" then you would need some method to transverse this plan and if u did, then we would easily be able to communicate, but we would at first sound like a wild animal. They either would ignore us, not understand or perceive us, or they would attempt to send back a signal (essential they are ET's)
IF you mean the second then thats some mystic stuff and its pretty creepy (although a fun read for me :P)
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