Simplify Write the Answer in Standard Form $\left( 2.1 \times 10 ^ { - 3 } \right) \left( 4 \times 10 ^ { - 2 } \right)$

Multiple Choice

Simplify. Write the answer in standard form.
- $\left( 2.1 \times 10 ^ { - 3 } \right) \left( 4 \times 10 ^ { - 2 } \right)$

A) $0.00084$
B) $0.0000084$
C) $0.00000084$
D) $0.000084$