A cyclotron with two cylindrical dees (shapes of D ), as shown in the figure, is used to accelerate proton of mass m=1.6×10−27kg and charge 1.6×10−19C by applying a potential difference of 100kV between the dees. A magnetic field of 1T is applied normal to the plane of dees of maximum radius of 50cm. The number of revolutions made by the protons just before coming out of the cyclotron will be about whenever a protons leaves one of the dees , other will kept at proper polarity, is