The earth's crust is broken up into a series of more-or-less rigid plates that slide around due to motion of material in the mantle below. Although the speeds of these plates vary somewhat, they are typically about 4.80 . Assume that this rate remains constant over time. 1-Los Angeles is presently 550km south of San Francisco, but is on a plate moving northward relative to San Francisco. If the 4.80cm/yr velocity continues, how many years will it take before Los Angeles has moved up to San Francisco?