At the melting point. Draw a line up from 0 degrees and a line to the right from 1 atm. They meet at the line between solid and liquid... the melting point
Answer and Explanation
The isomer picked is the N-Propylamine.
It has a lone pair of electron available on the electron rich Nitrogen and no formal charge.
Since it will be hard to draw the Lewis structure in this answer format, I'll attach a picture of the Lewis structure to this answer.
The lone pair of electron is shown by the two dots on the Nitrogen atom.
Answer:

Explanation:
Using Gay Lusaac's law where there is no change in Volume. The pressure changes directly proportional to absolute T°
P₁/T₁ = P₂/T₂
P₁T₂/T₁
P₂ = 
P₂ = 