(Solved): Last night, an astronomer observed a star in the Andromeda galaxy, which is 2.5 million light years ...

Last night, an astronomer observed a star in the Andromeda galaxy, which is 2.5 million light years away. After careful analysis of that starlight, she noticed that the star appears to have an age of 5.0 million years. We know that this type of star explodes when it reaches an age of 10 million years. How many million years will it be until the explosion of this star can be observed from Earth?