A rocket of mass `20kg` has `180kg` fuel. The exhaust velocity of the fuel is `1.6km//s`. Calculate the minimum rate of consumption of fuel so that the rocket may rise from the ground. Also, calculate the ultimate vertical speed gained by the rocket when the rate of consumption of fuel is `(g=9.8m//s^2)`
(i) `2kg//s` (ii) `20kg//s`