A piece of plumber's solder weighing 3.0gm was dissolved in dilute nitric acid, then treated with dilute ${\mathrm{H}}_2{\mathrm{SO}}_4$. This precipitated the lead as ${\mathrm{PbSO}}_4$, which after washing and drying weighed 2.93gm.The solution was then neutralized to precipitate stannic acid, which was decomposed by heating, yielding $1.27\mathrm{gm} {\mathrm{SnO}}_2$. What is the analysis of the solder? $\mathrm{Pb}=207.2\mathrm{amu},\mathrm{Sn}=118.7\mathrm{amu})$.