Complete Question 
Potassium is a crucial element for the healthy operation of the human body. Potassium occurs naturally in our environment and thus our bodies) as three isotopes: Potassium-39, Potassium-40, and Potassium-41. Their current abundances are 93.26%, 0.012% and 6.728%. A typical human body contains about 3.0 grams of Potassium per kilogram of body mass. 1. How much Potassium-40 is present in a person with a mass of 80 kg? 2. If, on average, the decay of Potassium-40 results in 1.10 MeV of energy absorbed, determine the effective dose (in Sieverts) per year due to Potassium-40 in an 80- kg body. Assume an RBE of 1.2. The half-life of Potassium-40 is  years.
years.
Answer:
The potassium-40 present in 80 kg is  
The effective dose absorbed per year is   per year
 per year 
Explanation:
 From the question we are told that 
       The mass of potassium in 1 kg of human body is 
       The mass of the person is 
        The abundance of Potassium-39 is   93.26%
         The abundance of Potassium-40 is   0.012%
          The abundance of Potassium-41 is   6.78 %
          The energy absorbed is  
Now  1 kg of human body contains        of  Potassium
 of  Potassium 
So      80 kg of human body contains      k kg of  Potassium 
=>   
      
Now from the question potassium-40 is  0.012% of the total  potassium so 
      Amount of potassium-40  present is mathematically represented as
             
             
The effective dose (in Sieverts) per year due to Potassium-40 in an 80- kg body is mathematically evaluated as 
            
Substituting values 
           
             
Converting to Sieverts
 We have 
            
            
            
So 
      for half-life ( )  the dose is
)  the dose is  
      Then for 1  year the dose would be  x
=>         
               per year
 per year