Answer:
The following are the answer to the given points:
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
<h2>This function will land up in infinite function call</h2>
Explanation:
first time when the function gets invoked,
f(6,8), so k=6 & n=8, inside the function it checks k==n, ie. 6==8, returns false, then one more if is available, so 6>8 is check for , once again it is false and else loop is executed, the function is called recursively using f(k-n,n), that is f(6-8,8), it means f(-2,8) is passed.
Second time,
if(-2==8) is false, so if(-2>8) is again false and function f(-10, 8) is called
if(-10==8) is false, so if(-10>8) is again false and function f(-18,8) is called
if(-18==8) is false, so if(-18>8) is again false and function f(-26,8) is called
So this goes recursively and ends in an infinite function call.