Consider the following radioactive decay process 
${ }_{84}^{218}\mathrm{A}\stackrel{\mathrm{\alpha }}{\to }{\mathrm{\alpha A}}_1\stackrel{{\mathrm{\beta }}^{-}}{\to }{\mathrm{A}}_2\stackrel{\mathrm{\gamma }}{\to }{\mathrm{A}}_3\stackrel{\mathrm{\alpha }}{\to }{\mathrm{A}}_4\stackrel{{\mathrm{\beta }}^{+}}{\to }{\mathrm{A}}_5\stackrel{\mathrm{\gamma }}{\to }{\mathrm{A}}_6$
The mass number and the atomic number of A₆ are given by: