The mass would be 51 kg. So b is the right answer.
B. Impedes the flow of electrons
Answer:
t = 25.5 min
Explanation:
To know how many minutes does Richard save, you first calculate the time that Richard takes with both velocities v1 = 65mph and v2 = 80mph.

Next, you calculate the difference between both times t1 and t2:

This is the time that Richard saves when he drives with a speed of 80mph. Finally, you convert the result to minutes:

hence, Richard saves 25.5 min (25 min and 30 s) when he drives with a speed of 80mph
Because fossil fuels are non-renewable resources.
This means, if we run out, we will not be able to reproduce it.
It would be the last that exists. (For oil, it'd be for the next few hundred years.)