Answer:
the mass of the body is 0.02 kg.
Explanation:
Given;
relative density of the oil,
= 0.875
mass of the object in oil,
= 0.013 kg
mass of the object in water,
= 0.012 kg
let the mass of the object in air = 
weight of the oil, 
weight of the water, 
The relative density of the oil is given as;

Therefore, the mass of the body is 0.02 kg.
isotopes are the same element, but have different numbers of neutrons (but still have the same number of electrons and protons), hence have a different mass number.
The law of conservation of energy<span>, a fundamental concept of physics, states that the total amount of </span>energy<span> remains constant in an isolated system. It implies that </span>energy<span> can neither be created nor destroyed, but can be change from one form to another.</span>
Their atomic number?? (easy guess)