A high-energy neutrino beam is passed through a slab of aluminum-27 (with 27 nucleons in each nucleus) of thickness 71.1 cm. The probability that a neutrino in the beam will scatter off a nucleon in the aluminum slab is 6.00-10-12. The scattering cross section is given by σ(E) = (0.68∙10-38 cm2 GeV-1)E, and aluminum has a density of 2.77 g/cm3. What is the energy (in GeV) of the neutrino beam?