Use Scientific Notation to Solve the Problem $7 \times 10 ^ { 13 }$

Multiple Choice

Use scientific notation to solve the problem.
-If you could generate energy by fusing the hydrogen in ordinary tap water, how much water would you need to meet the energy needs of the United States for 35 years? Assume that the energy Released by fusion of hydrogen in one liter of water is $7 \times 10 ^ { 13 }$ joules and that the U.S. annual Energy consumption i $1 \times 10 ^ { 20 }$ joules. Give your answer in scientific notation.

A) $5 \times 10 ^ { 7 }$ liters
B) $5 \times 10 ^ { - 7 }$ liters
C) $5 \times 10 ^ { 1.5 }$ liters
D) $1.4 \times 10 ^ { 7 }$ liters