The administrator modifies a rule on the firewall and now all the ftp users cannot access the server any longer. the manager calls the administrator and asks what caused the extreme downtime for the server. in regards to the manager's inquiry, what did the administrator forget to do first?

Acomputer has a two-level cache. suppose that 60% of the memory references hit on the first level cache, 35% hit on the second level, and 5% miss. the access times are 5 nsec, 15 nsec, and 60 nsec, respectively, where the times for the level 2 cache and memory start counting at the moment it is known that they are needed (e.g., a level 2 cache access does not even start until the level 1 cache miss occurs). what is the average access time?