In the itv$4$ network, the x & $\frac{?}{{?}_{?}}$ University is responsidie tor a $/$ Io network diock tnat contains $2^{16}$ IP addresses. This network has no active host. An attacker in the Internet triggers a syn$-$flood attack against a website, whose IP address is denoted as "aaa.bbb$.$ccc$.$ddd$".$ The source IP address of each attacking TCP SYN packet is randomly generated. The XYZ university has observed totally $W$ unsolicited TCP SYNACK packets with the source IP address of "aaa.bbb$.$ccc$.$ddd$".$

Which of the following expressions best estimates the number of TCP SYN packets generated by this attacker against that website?

$W{2}^{16}$

$W{2}^{24}$

$W(\frac{2^{32}}{2^{24}})$

$W(\frac{2^{24}}{020})$