(4.0 x 10^12) x (2.5 x 10^-6)

Oops! Error on line 8 there, Melody.

I know you included that deliberately, just to see who is following along.

$$\\(4.0 \times 10^{12}) \times (2.5 \times 10^{-6})\\\\
=4.0 \times 10^{12} \times 2.5 \times 10^{-6}\\\\
=4.0 \times 2.5\times 10^{12} \times 10^{-6}\\\\
=4.0 \times 2.5\times 10^{12-6} \\\\
=10\times 10^{12-6} \\\\
=10^1\times 10^{12-6} \\\\
= 10^{12-6+1} \\\\
= 10^{\textcolor[rgb]{1,0,0}{7}} \\\\
=\textcolor[rgb]{1,0,0}{10,000,000}$$

All fixed, thanks anon :)