On average, one call arrives every $5$ secoods$.$ During a period of $15$ seconds, what is the probahility that no call arrives?

A$.0\mathrm{.}135$

B$.0\mathrm{.}050$

C$.0\mathrm{.}270$

D$.0\mathrm{.}365$

Given that MTBF $-1000$ hours and MTTR $-3$ hours, what is the unavailability of a single processor for $10$ years?

A$.26\mathrm{.}2\mathrm{.}8$ hours

B$.350\mathrm{.}5$ hours

C$.57\mathrm{.}6$ minutes

D$.250$ mitutes

Inden Number $q,$

$44.$ What combination switching does a C$-$DOT enploys?

A$.$ sTSTSS

B$.$ TSST

C$.$ TSSSsI

D$.$ TST

$45.$ With $......$ the node does not need to make a routing decision for cach packet

A$.$ Virtual circuit

H$.$ Message switching

C$.$ Circuit switching

D$.$ Datagram

$46.$ Teletraftic models are

A$.$ Deterministic

B$.$ Constant

C$.$ Stochastic

D$.$ Variable

$47.$ An exchange serves $3,000$ subscriben. If the buny hour call attempe $($BHCA$)$ is $20,000$ and the call completion rate is $60\%,$ calculate the busy hour calling rate.

A$.1$

B$.2$

C$.3$

D$.4$

$48.$ Duriag the buay haur, $500$ calls arrive at an cachange. The average halding time is three minutes. What is the offered traffic in CCS$?$

A$.25$

B$.1,500$

C$.600$

D$.900$

$49.$ In a wirelen network each subscriber generates three calla per hour on the inveruge and a typical call holding time is $240$ seconds. What is the truffic intensity in Erlangs?

A$.0\mathrm{.}20$

i$.0\mathrm{.}10$

C$.0\mathrm{.}05$

D$.0\mathrm{.}15$

Indes Number

$50.$ The hanic mesure of performunce for a loss system is the $q,$

A$.$ waiting time