The value of 3⁵¹ mod 5 is_________.

In an RSA cryptosystem, the value of the public modulus parameter n is 3007. If it is also known that $$\varphi $$(n) = 2880, where $$\varphi $$() denotes Euler's Totient Function, then the prime factor of n which is greater than 50 is ______.

Consider that 15 machines need to be connected in a LAN using 8-port Ethernet switches. Assume that these switches do not have any separate uplink ports. The minimum number of switches needed is _____.

Which of the following protocol pairs can be used to send and retrieve e-mails (in that order)?