A medical technician is working with the four samples of radionuclides listed in the table below. Initially, each sample contains of ... ?

A medical technician is working with the four samples of radionuclides listed in the table below. Initially, each sample contains 20.00 umol of the radionuclide.
First, order the samples by decreasing initial radioactivity. Then calculate how long it will take for the amount of radionuclide in each sample to decrease to 1/32  of the initial amount.

Michael2021-04-07T03:14:10Z

The shorter the half-life the higher the initial radioactivity
 
A 4
B 1
C 3
D 2
----------------------
 
1/32 = (1/2)⁵ 
 
Therefor
1/32 is 5 half-lives
 
A = 25 years
B = 85 hours
C = 15 years
D = 130 hours