Two intermetallic compounds, $AB$ and $A{B}_2,$ exist for elements A and $B.$ If the compositions for $AB$ and $A{B}_2$ are $34\mathrm{.}3wt\%A-65\mathrm{.}7wt\%B$ and $20\mathrm{.}7wt\%A-79\mathrm{.}3wt\%B,$ respectively, and element A is potassium, identify element B $.$

Phosphorus

Arsenic

Antimony

Sulfur