The fоllоwing questiоns refer to the diаgrаm below, which shows а market's cost and revenue curves. A graph in the first quadrant is shown with price of good X on the vertical axis and quantity of good X on the horizontal axis. Values P 1, P 2, P 3, and P 4 are labeled from bottom to top on the vertical axis, and values Q 1, Q 2, and Q 3 are labeled from left to right on the horizontal axis. A straight, increasing line labeled marginal social cost is drawn that passes through points Q 1 and P 2, Q 2 and P 3, and Q 3 and P 4. A second parallel line labeled marginal private cost is drawn below the first line and passes through points Q 2 and P1, and Q 3 and P 2. A curve labeled marginal social benefit is also drawn starting in the upper left corner of the graph that is decreasing and concave up, and passes through points Q 1 and P 4, Q 2 and P 3 where it intersects the marginal social cost curve, and Q 3 and P 2 where it intersects the marginal private cost curve. Dashed horizontal and vertical reference lines are drawn from each labeled value on the axes. Points on the curves are marked at the coordinates Q 1 and P 2, Q 1 and P 4, Q 2 and P 1, Q 2 and P 3, Q 3 and P 2, and Q 3 and P 4. The socially optimal quantity and the per-unit tax that will achieve the socially optimal quantity are which of the following?