In a series RC circuit, the voltage across the capacitor during charging and discharging can be modeled by exponential functions of time. The exponential time constants of charging (τcharge) and discharging (τdischarge) are related by:

According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?