A water reservoir is 3 m deep. When a sphere of diameter 0.2 mm and 12 × 103 kg/m3 dense is dropped in it, the sphere attains uniform velocity after travelling 1 m in 7 seconds. Find the total time (t) (in secs) taken by the sphere to reach the bottom of the reservoir. Use cD = \(\frac{24}{R_e}\) and dynamic viscosity = 10-3 Kg/ms