A certain local area network has been running for 2 years (17,520 hours), but it was stopped for 6 hours due to equipment failure. Later, after the network was expanded and new equipment was added, it ran for another year (8,760 hours), and was stopped for another 4 hours due to software failure. Which of the following statements are correct about the availability of this network? (Multiple choice)

A certain local area network has been running for 2 years (17,520 hours), but it was stopped for 6 hours due to equipment failure. Later, after the network was expanded and new equipment was added, it ran for another year (8,760 hours), and was stopped for another 4 hours due to software failure. Which of the following statements are correct about the availability of this network? (Multiple choice)
A . Availability after network expansion is better than before expansion
B. Availability after network expansion is worse than before expansion
C. Before the expansion, the network availability was 99.97%
D. The availability of the network has been 99.99% since it was started

Answer: BC