Equal volumes of Hydrochloric acid of ${\mathrm{P}}^{\mathrm{H}}=2$ is mixed with barium hydroxide solution of ${\mathrm{P}}^{\mathrm{H}}=12$. The concentration of barium chloride in mixed solution is $\mathrm{p}\times {10}^{-3}\mathrm{M}$ (in scientific notation). What is the value of 2p?