The equation that models Pluto's elliptical orbit around the sun is ((x - 0.9)²)/(12.96) + (y²/12.15) = 1 in billions of miles. If the sun is located at one focus and its coordinates are (0,0), find Pluto's farthest distance from the sun in billions of miles.
A - 13.2
B - 14.4
C - 15.6
D - 16.8