A
carbon
atom
has
a
relative
atomic
mass
of
13.5.
60%
of
the
carbon
atom
has
a
mass
number
of
12.9,
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
13.5
atom.
Give
your
answer
to
2
decimal
places
if
needed.