Potassium-40 decays into argon-40 by electron capture with a half-life of 1.28x10^9 years. THis decay forms the basis of the potassium-argon dating method that is used with igneous rocks. This method assumes that no argon was trapped in the rock when it was formed frothe molten material. A meteorite was found to have equal amounts of 40K and 40Ar. a) Of the potassium-40 that was originally present, what fraction has decayed? b) how long ago was this meteorite formed