Incompressible & Compressible Aerodynamics

A stationary two stage rocket with initial mass of 16000kg, carrying a payload of 1000kg, is fired in a vertical trajectory from the surface of the earth. Both the stages of the rocket have same specific impulse, Isp, of 300s and same structural coefficient of 0.14. The acceleration due to gravity is 9.8m/s2. Neglecting drag and gravity effects and considering both the stages with same payload ratio, the terminal velocity attained by the payload in m/s is __________________.