Seraphina is driving two hours to visit her family. For the first hour, she traveled at a speed of 61 miles per hour. Then, in the second hour, she traveled at a speed of 73 miles per hour. What is the percentage increase of Seraphina's speed? If necessary, round to the nearest tenth of a percent. A. 80.3% B. 19.7% C. 16.4% D. 83.6%