A 4.6-mm-diameter proton beam carries a total current of 1.8 mA . The current density in the proton beam, which increases with distance from the center, is given by J=Jedge(r/R) , where R is the radius of the beam and Jedge is the current density at the edge. Part A How many protons per second are delivered by this proton beam? Express your answer using two significant figures.