A radial burning solid propellant rocket has a hollow cylindrical grain. The inner diameter of the grain is 30 mm and the outer diameter is 100 mm. The length of the grain is 0.5 m. The throat diameter of the nozzle is 12 mm. If the burn rate of the propellant in mm/s is given by the law r = 0.019 p^0.38, where p is the pressure in Pa, determine: a. The thrust soon after ignition (initial thrust) and the thrust at burnout
b. The maximum value of chamber pressure
c. The burning duration
d. The time taken for the chamber pressure to fall from the maximum to 10% of the maximum (tail-off).