SOLUTION
The equation for this question should be
[tex]200\times2^h=6400[/tex]Solving for h, we have
[tex]\begin{gathered} 200\times2^h=6400 \\ \text{dividing both sides by 200 we have } \\ \frac{200\times2^h}{200}=\frac{6400}{200} \\ 2^h=32 \end{gathered}[/tex]This becomes
[tex]\begin{gathered} 2^h=32 \\ 2^h=2^5 \\ \text{cancelling bases of 2, we have } \\ h=5 \end{gathered}[/tex]Hence the answer is 5 hours. The answer is option D
