There are three different time periods. You will have to set up an equation to describe what happens in each of them. First, write down an equation to describe the 400 minute decay of the cup of coffee left in the pot.

You should have come up with:

 [1] 
Where N0 is one quarter of the initial amount in the pot. It is lp because there are no biological eliminations for the pot i.e. lb = 0

Next, you should be able to get an equation to describe the 360 minute time the isotope was in the owl. The effective half-life in the owl is 4.00 hours, or 240 minutes. Therefore the effective half-life in the owl will be

and

 [2] 

Where N'0 is the amount in both bats at the moment they are eaten. Therefore 0.5N'0 is the final amount in the bat.
Next, you need an equation for the 40 minutes after the bats drank the coffee and before they are eaten.
 

 [3] 

From [2] N'0 = 566 {Answer to (a)}
Using this in [3]
N0 = 400
So the initial amount in the pot was 4X400 = 1600 counts per minute. {Answer to (b)}
Now using [1]
lp = (0.693)/400 = 1.73X10-3  min-1 {Answer to (c)}

The fourth and final equation you will need relates the three decay constants to each other.

[4] effpb

lbB = le -lpB  = (8.66 - 1.73)X10-3 min-1  {Answer to (d)}

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