A gamma-ray telescope intercepts the pulse of gamma radiation from a magnetar, a kind of star having a spectacularly big magnetic field. The pulse lasts 0.10 s and delivers 7.7 x 10-6 J of energy perpendicularly to the 99-m2 surface area of the detector of telescope. The magnetar is thought to be 3.74 x 1020 m (around 40000 light-years) from earth, and to encompass a radius of 8.5 x 103 m. Determine the magnitude of the rms magnetic field of the gamma-ray pulse at the surface of magnetar, supposing that the pulse radiates evenly outward in all directions. (Suppose a year is 365.25 days.)