Consider a network containing $200$ hosts. Each host runs $3$ network applications $($a file sharing application, voice call application, and instant messaging application$),$ and each application should be able to communicate with the corresponding application on any other host $($e$.$g$.$ voice on host $1$ with voice on host $2$; but not voice on host $1$ with file sharing on host $2).$

If symmetric key security is required in the network, what is the maximum number of session keys needed?

Select one:

a$.19900$

b$.4950$

c$.200$

d$.600$