Antineutrinos, electrons and protons colliding, O MY!?

In a process known as beta decay, a neutron in an unstable atomic nucleus becomes a proton, in the process ejecting an electron and an antineutrino. (a) Use conservation of charge to determine the charge of an antineutrino. (b) Sixty billion neutrinos (mostly from the Sun) p through every square centimeter on Earth every second. They are hardly noticeable due to their negligible m and weak interaction with matter. When a neutrino and an antineutrino collide, however, they annihilate each other and produce two (electrically neutral) gamma rays traveling in opposite directions. What is the charge of a neutrino?