Utilization of ethernet is
U= 100 * (F/R) / (F/R + T*C) ------------------ @1
U= Percent Utilization
R = Transmission Rate = 10 Mbps
F = Number of bits in a frame = 512 bytes = 4096 bits
T = Slot Time = 51.2 micro sec
C = Number of Contention Intervals = $(1-1/N)^(1-N)$ - 1 = 1.716
N = Number stations = 500
F/R = 4096/10* $10^{6}$ = 409.6 micro sec
put in the 1,
U = (100*409.6)/(409.6+(51.2*1.716))
= 82.33 $\approx$ 82 % utilization
Option D
See this - http://www.piya.ee.engr.tu.ac.th/course/le517/lecture_10.pdf