$($Please keep answer short$)$

$1)$ What is the fundamental difference between a fat$-$client and a thin$-$client approach to client$$server systems architectures?

$2)$ Give two advantages and two disadvantages of decentralized and semi$-$centralized peer$-$to$-$peer architectures.

$3)$ Explain why deploying software as a service can reduce the IT support costs for a company. What additional costs might arise if this deployment model is used?