Which layer of the OSI $7-$layer model is responsible for each of the following functions?

a$.$ Determining the best path to route packets.

b$.$ Provides quality of service $($QoS$)$ and reliable end$-$to$-$end transfer of data.

c$.$ Error control over a single hop physical link

d$.$ Transfer of bits between adjacent devices.

e$.$ Defines the format$/$representation of the data