[25 points] Fill out the following table for the given memory reference stream on a busbased shared-memory machine that supports the Dragon protocol. Show the state transition of each processor and the bus transactions. All of the references are to the same memory location X:r/w indicates read or write, and the digit refers to the processor issuing the reference, e.g., r1 means processor P1 reads X. Assume that all caches are initially empty, and all caches are write-allocated. r1,r2,w3,r2,r3,w2,w1,r1,r2,r3