"How can you be so calm?"

Translation: Kiel vi povas esti tiel trankvila?

[person594]

why is "tiom trankvila" incorrect?

[mihxal]

You can report this.

[M.A.James]

Why is "do trankvila" also incorrect?

[Ungewitig_Wiht]

I think that tiel and do are two different meanings of so in english.