Your organization uses an $802\mathrm{.}11$b wireless network. Recently, other tenants installed the following equipment in your building:

A wireless television distribution system running at $2\mathrm{.}4$ GHz$.$

A wireless phone system running at $5\mathrm{.}8$ GHz$.$

A wireless phone system running at $900$ MHz$.$

An $802\mathrm{.}11$a wireless network running in the $5\mathrm{.}725-5\mathrm{.}850$ GHz frequency range.

An $802\mathrm{.}11$j wireless network running in the $4\mathrm{.}9-5\mathrm{.}0$ GHz frequency range.

Since this equipment was installed, your wireless network has been experiencing significant interference. Which system is to blame?

answer

The $802\mathrm{.}11$j wireless network

The $900$ MHz wireless phone system

The wireless TV system

The $802\mathrm{.}11$a wireless network

The $5\mathrm{.}8$ GHz wireless phone system