The answer is C. Natural gas because both A and B are their own forms of energy.
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:
The drag coefficient is
Explanation:
From the question we are told that
The density of air is 
The diameter of bottom part is
The power trend-line equation is mathematically represented as

let assume that the velocity is 20 m/s
Then


The drag coefficient is mathematically represented as

Where
is the drag force
is the density of the fluid
is the flow velocity
A is the area which mathematically evaluated as

substituting values


Then

It's a Newton Meter Those two are multiplied to get a joule.