at t=0 collision occur . and X draws k=1 and Y draws
k=2 . (but question doesn't tell what node X and Y draw
K value in sub-sequent collisions , it say only k value can be random)
best case :
1st collsion : X draws k=1 and Y draws k=2 (given)
after 8 microsecond , node x can transmit the frame.
but it can transmit and send last bit of frame upto
16 microsecond. becuse after that , node y again try to
transmit the frame and collision happen . so in
16-8-4(propagation time )=4 microsec, node x can transmit
only 4*150 mbps=600 bit .
2nd collision: now let x draw =1 and y draw 3 or 4 becuse at
2nd tym collision , for node Y , n=2 so k ranges {1,2,3,4}
. let assume 3 . so after another 8 microsec i.e after t=24 microsec
,node x again start transmission . and node y start transmission again
after 24 microsec . so in 24-8-4=12 microsec , node x can transmit
12*150=1800 bit . but only 900 bits frame is left . so transmission time
will be= 6 microsec
so total time taken by node X to completely deliver the frame to node Y
is= 8+4+8+6+2*4=34 microsec
worst case :
in the worst case , we can assume everytime when collision happen after
t=0 , node x draws k value 1 and node y draws k value 2 . then total time taken by
node x to complete deliver the frame to node y =8+4+8+4+8+2+3*4=46 microsecond