Question 852441
Initial amount:
{{{A(0)=2800*(1/2)^0=2800*1=2800}}}
 
After 40 hours:
{{{A(40)=2800*(1/2)^(40/14)}}}
My calculator says 0.5^(40/14) is 0.138, and
{{{A(40)=386}}}
(I believe it because 40/14 is about 3, and (1/2)^3=1/8=0.125).