Answer:
The following are the answer to the given points:
Step-by-step explanation:
In point (a):
Calculating the long-distance call cost:

Calculating the local call cost:

Calculating the overall cost of PSTN:

In point (b):
Calculating the call rate per second and the average arrival rate:

The call average length:
The complete agent number:

The strength of traffic:
The occupancy of the agent:

Calculation of obtained:

We get = 0.329 to substitute values.
In point (c):
The rate of blocking =

average call time


In point (d):
Calculating the number of link, which is required:
In point (e):
Calculating the Line Number:
PSTN line number:

In point (f):
The gross design expense = $ 2309. 5