In order to measure the cross section of the reaction of Example 13.2, a detector subt...

In order to measure the cross section of the reaction of Example 13.2, a detector subtending a solid angle of is used at the scattering angle particles is incident on a¹²C target of thickness for one hour. If the differential cross section is 0.2 mb/sr, how many protons are detected at the angle θ?