Passage During Deep Underwater Dives, Scuba Divers Must Overcome the External

Passage
During deep underwater dives, scuba divers must overcome the external ambient pressure in order to expand their chests to inhale.  To assist underwater breathing, air from scuba tanks is administered at high pressures to keep divers' lungs inflated.  Scuba tanks are often filled with a mixture of N₂ and O₂ gas.  Due to the increased pressure of the gases in the lungs, a greater amount of the gases are dissolved into the bloodstream during underwater dives.  At a body temperature of 37°C, the solubility of N₂ gas in blood is 6.0 × 10⁻³ mol/L⋅atm and the solubility of O₂ gas is 1.3 × 10⁻² mol/L⋅atm.If a diver ascends too quickly after an extended dive, there is an increased risk of vascular bubble formation.  Due to the decrease in ambient pressure, the excess gas dissolved in the blood may come out of solution as gas bubbles and cause a number of adverse effects.  This condition is known as decompression sickness, or "the bends."  To avoid this problem, scuba divers limit their rate of ascension to allow the excess gas dissolved in their blood to be safely removed through respiration.  Because gas bubbles are good reflectors of sound, these bubbles can be detected using Doppler ultrasonic flowmetry after the diver has surfaced.
Adapted from M. Spencer, Journal of Applied Physiology. ©1976 American Physiology Society.
-While underwater, divers designate their position with a buoy that floats at the surface above them.  Assuming the buoy is not pulled by the diver, what is the mass of a floating buoy that experiences a buoyancy force of 10 N and is 20% submerged?

A) 1 kg
B) 2 kg
C) 5 kg
D) 10 kg