Atmospheric Pressure in Interstellar Space Is Approximately 1 × 10^-17

Atmospheric pressure in interstellar space is approximately 1 × 10^-17 torr at a temperature of -173 °C. How many gas molecules are present in 25,000 L of interstellar space (about the volume of a bedroom) ?

A) 2 × 10⁷ molecules
B) 4 × 10^-17 molecules
C) 2 × 10¹⁰ molecules
D) 3 × 10^-14 molecules