A massless spring of constant 64N/m is attached vertically to a table. A 7-g balloon is filled with helium (density = 0.180 kg/m3 ) to a volume of 1.6m³ and is then connected to the spring, causing it to stretch. After this system reaches equilibrium, the spring (with a balloon) is further stretched by 5cm and released. Find the period of spring oscillations about the equilibrium. Take air density to be 1.225 kg/m³. Neglect the air resistance. State your answer to the nearest 0.001s.