Chapter 5 - Section 5.2 - More Work with Exponents and Scientific Notation - Exercise Set - Page 268: 70

$2.16\times10^{-2}$

Using laws of exponents, the given expression simplifies to \begin{align*} & (3.6\times10^{-12})(6\times10^{9}) \\\\&= (3.6\times6)(10^{-12}\times10^{9}) \\\\&= 21.6\times10^{-12+9} \\\\&= 21.6\times10^{-3} \\\\&= 2.16\times10^{-2} .\end{align*}