+2 electron charges = 2x1.6x10^-19Coulombs
Take the stone's position at ground level to be the origin, and the downward direction to be negative. Then its position in the air 
at time 
is given by
Let 
be the depth of the well. The stone hits the bottom of the well after 5.00 s, so that
Iodine-131 has a half life of 8 days, so half of it is gone every 8 days.
10 grams of iodine-131 is left for 24 days.
At 8 days: 10/2=5 grams left
At 16 days: 5/2=2.5 grams left
At 24 days: 2.5/2=1.25 grams left.
**
Your mistake is that you stopped at 16 days.
Honest, the map is so tiny, and so fuzzy when I blow it up, I really can't see anything on it clearly. But I think maybe I do see a letter ' C ' in the eastern Mediterranean, with a curved line over to the southern Gaza strip, where it meets Sinai. So I'll say it's the Gaza Strip.
