Multimedia Communications plz answer!!!!

Q1: (i) Identify and explain the meaning of the key QoS parameters associated with the circuit-switched network types. (ii) Derive the maximum block size that should be used over a channel which has a mean BER probability of 0.00025 if the probability of a block containing an error - and hence being discarded is to be 0.15. Hint: PB=1(1P)N Q2: Determine the propagation delay associated with the following communication channels: (i) a connection through a private telephone network of 3.5km, (ii) a connection through a PSTN of 250km, (iii)a connection over a satellite channel of 65000km. Assume that the velocity of propagation of a signal in the case of (i) and (ii) is 2108m/sec and in the case of (iii) 3108m/sec. Q3: A file of 200Mbytes of size is being retrieved from a Web server. Assuming negligible delays within the server and trunk network, Calculate the data transfer rate over the following types of access circuits (i) PSTN modem operating at 56kbps, (ii) an aggregated basic rate access line of 128kbps, (iii)a cable modem operating at 27Mbps