The position as a function of time for your dog as it chases a ball across the yard is r = (0.9 + (0.7m/s2) 12)i + (4.6 mls) ti, where the origin is the northeast corner of the yard. Find the average speed of the dog between t = 0.0 s and t = 3.0s. Select one: O a. 5.1 m /s O b. 9.3 m /s O c. 2.3 m /S O d. 7.4 m /s