Oscar is in the school’s cross country team. His coach clocks his time to determine how fast he runs. For the first 15 minutes, Oscar runs at a uniform speed of 13 miles per hour. For the next 30 minutes, his speed slows down at a constant rate. During the last 45 minutes of the race, his speed continued to fall but not as much as it was between 15’th to 45’th minute of the race. Which of the following graphs describes Oscar's speed w.r.t to time appropriately?