Rewrite the Number or Expression as Requested $\left( 4 \cdot 10 ^ { 10 } \right) \cdot \left( 7 \cdot 10 ^ { 12 } \right)$

Multiple Choice

Rewrite the number or expression as requested.
-Rewrite the number or expression as requested.
$\left( 4 \cdot 10 ^ { 10 } \right) \cdot \left( 7 \cdot 10 ^ { 12 } \right)$ (Write the result in scientific notation.)

A) $2.8 \cdot 10 ^ { 22 }$
B) $2.8 \cdot 10 ^ { 23 }$
C) $2.8 \cdot 10 ^ { 21 }$
D) $28 \cdot 10 ^ { 23 }$