To get to the answer, we'll have to multiply the pieces of mail delivered each second by the amount of seconds in 6 days. This is,
[tex]\begin{gathered} (2^4\times3\times5^3)\times(2^8\times3^4\times5^2)^{} \\ \rightarrow2^4\times3\times5^3\times2^8\times3^4\times5^2^{} \end{gathered}[/tex]Using power properties,
[tex]2^4\times3\times5^3\times2^8\times3^4\times5^2\rightarrow2^{12}\times3^5\times5^5[/tex]Therefore,
[tex]2^{12}\times3^5\times5^5[/tex]pieces of mail are delivered by the United States Postal Service in 6 days.