A half-cache Mystery Cache

This is my first cache posted ever!!! THANK YOU BIRK FOR THE CACHE!!

And as such, i decided to theme it after something i like, Math 😱 

The cache is NOT at the posted coordinates, so in order to get the coordinates, you need to solve 2 problems! For the problems, theres an easy formula you can find online to help you if you need it! Another thing is that you need to write your user on the log, or else... and lastly BYOP!!!!!!

Question A

You have an element that has a half life of every 0.5 seconds. If, after 2.5 seconds, your element only has 1.25 grams remaining what was the original mass?

Question B

You have an element that has a half life of 7 years. If you have a sample of 5.552 grams, how many grams will remain after 28 years?

61 21.8(A - 1)

-149 33(B)