There is pb$2+,$mg$2+,$zn$2+$ in $0\mathrm{.}4085$ g sample. The sample solution is first treated with Cn$-$ to mask the Zn$2+$ ions. In the titration of Mg$2+$ and pb $2+,42\mathrm{.}22$ ml of $0\mathrm{.}2064$ M edta is consumed. BAL is added to this solution and the resulting Y$4-$ is titrated with $19\mathrm{.}35$ ml of $0\mathrm{.}007657$ Mg$2+.$ Finally, with the addition of formaldehyde, the Zn$2+$ mask is removed and $28\mathrm{.}63$ ml Edta is spent for titration. Find the percentage composition of the sample.

$($BAL makes a selective complex with pb$2+.)$