Identify each of the following as either scientific or engineering notation.

$2\mathrm{.}45{10}^2$

$26\mathrm{.}5{10}^{-3}$

$6\mathrm{.}67{10}^{-11}$

$3\mathrm{.}14159{10}^4$

$31\mathrm{.}4159{10}^3$

CO$2,$ W$18$