A carbon atom has a relative atomic mass of
13.3. 60% of the carbon atom has a mass
number of 12.7, 30% of the carbon atom has a
mass number of 13.6, whilst the remaining 10%
has a mass number which is not known.
Calculate the mass number of the carbon isotope
which is 10% of the Carbon 13.3 atom.
Give your answer to 1 decimal place.