Which of the following is/are example(s) of stateful application layer protocols?

(i) HTTP
(ii) FTP
(iii) TCP
(iv) POP3

Consider that B wants to send a message m that is digitally signed to A. Let the pair of private and public keys for A and B be denoted by $$K_x^ - $$ and $$K_x^ + $$ for x = A, B, respectively. Let K_x(m) represent the operation of encrypting m with a key K_x and H(m) represent the message digest. Which one of the following indicates the CORRECT way of sending the message m along with the digital signature to A?

A processor can support a maximum memory of $$4$$ $$GB,$$ where the memory is word-addressable (a word consists of two bytes). The size of the address bus of the processor is at least ___________ bits.

The stage delays in a $$4$$-stage pipeline are $$800, 500, 400$$ and $$300$$ picoseconds. The first stage (with delay $$800$$ picoseconds) is replaced with a functionally equivalent design involving two stages with respective delays $$600$$ and $$350$$ picoseconds. The throughput increase of the pipeline is percent.