A person is walking in downtown Chicago. He starts 7 blocks north and 3 blocks west of the city's center. He then walks to a position of 12 blocks north and 1 block east of the city's center. What was his displacement magnitude and direction?
O A. magnitude: 16.2 blocks; direction: -68.2 east of north
B. magnitude: 19.1 blocks; direction: -6.01 east of north
O C. magnitude: 6.40 blocks; direction: 51.3* east of north
O D. magnitude: 6.40 blocks; direction: 38.7" east of north