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.