This is a small part of a homework problem in which I need to calculate neutron flux. I have the neutron beam hitting a copper target, and two reactions take place Co-59(n,p)Co60metastable (cross section=19barn) and Co-59(n,p)Co60ground (cs=18barn). What is the cross section overall? Do I simply say there is a 18+19=37 barn cross section overall? I'm not so sure, it makes sense to add them thinking about it from a probability standpoint, but from an area of target standpoint, I think it should be somewhere between 18 and 19. Any thoughts? Thanks.