Two agents $A$ and $B$ have utilities $u_A = x_A + y, \qquad u_B = 2x_B + y,$ where $x_A, x_B$ are amounts of a private good and $y$ is the amount of a public good. Production satisfies $y + m(x_A + x_B) = 1$, with $m \in (0,1)$. Suppose a social planner decides that one unit should be produced. For what value of $m$ will the resulting allocation be Pareto optimal?