Answer:
Given
Per Kg of body mass, there is 3 gram of potassium
And abundance of three isotopes are as follows
Potassium-39, Potassium-40, and Potassium-41. Have abundances respectively as 93.26%, 0.012% and 6.728%.
1) A body weighing 80 Kg will have 240 grams of potassium. And the amount of Potassium-40 will be 0.012% of 240 gram
= 240*0.012/100 = 0.0288 gram.
2) Dose in (Gy) = (energy absorbed)/(mass of the body) = ( 1.1*106*1.6*10-19)/(80) = 22*10-10 J/kg
Dose (in siverts) = RBE*Dose(in Gy) = 1.2*22*10-10 = 26.4*10-10