Incompressible & Compressible Aerodynamics

The propellant in a single stage sounding rocket occupies 60% of its initial mass. If all of it is expended instantaneously at an equivalent exhaust velocity of 3000 m/s, what would be the altitude attained by the payload when launched vertically? [Neglect drag and assume acceleration due to gravity to be constant at 9.81 m/s 2.] (A) 315 km (B) 335 km (C) 365 km (D) 385 km