Consider the "exactly once" semantics with respect to the rpc mechanism. does the algorithm for implementing this semantic execute correctly even if the ack message sent back to the client is lost due to a network problem? describe the sequence of messages, and discuss whether "exactly once" is still preserved.

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?

If an appliance consumes 500 w of power and is left on for 5 hours, how much energy is used over this time period? a. 2.5 kwh b. 25 kwh c. 250 kwh d. 2500 kwh

A. in packet tracer, only the server-pt device can act as a server. desktop or laptop pcs cannot act as a server. based on your studies so far, explain the client-server model.