1.) the objects have the same temperature
this is the answer because thermal equilibrium is when two substances touch and the temperature becomes the same.
 
        
             
        
        
        
To find the temperature it is necessary to use the expression and concepts related to the ideal gas law.
Mathematically it can be defined as

Where
P = Pressure
V = Volume
n = Number of moles
R = Gas constant 
T = Temperature
When the number of moles and volume is constant then the expression can be written as

Or in practical terms for this exercise depending on the final temperature:

Our values are given as

Replacing

Therefore the final temperature of the gas is 800K