What is the temperature of a gas in which the atoms are moving very very slowly?

Cold.
Example: A frozen object (such as ice) is solid. Its molecules move extremely slow because the object itself isn't moving... It's like the skin on your bod... Imagine that wiggling and writhing on your bones. It's not like a gas, that can move freely and has no specific form or hold.
So again, the answer is Cold. 

Are there options for this?

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2   where t1=temperature of cold reservoir ( ° k) = 135            t2=temperature of hot reservoir ( ° k)   = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58%  note: this is the theoretical maximum efficiency of a perfect heat engine.   real-life engines do not achieve this value.