I pretty sure number 3 is false
Answer:

Explanation:
Given that,
Efficiency of heat engine, 
Temperature of hot source, 
We need to find the temperature of cold sink i.e.
. The efficiency of heat engine is given by :




So, the temperature of the cold sink is 256.2°C. Hence, this is the required solution.
Answer: 4
Explanation: I watched them win their 3rd and 4th
When sounds at two different frequencies are combined,
two new sounds are created ... at the sum and difference
of the original frequencies.
Combining two sounds at 490 Hz and 488 Hz creates
beats at 978 Hz and 2 Hz.
The fluttering "wah wah" effect of the 2 Hz beat is much more
noticeable than the new sound at 978 Hz.