The government needs to raise $16000$ in order to fund a new subsidized housing building. To raise the money, they can either put a per-book tax on the book market, where supply and demand are both relatively elastic, or they can put a per-cigarette tax on the cigarette market. Assume neither tax can be greater than $10$.
In the end, they decide to tax the book market, because the deadweight loss that goes along with a tax capable of raising $16000$ is smaller than the deadweight loss that goes along with a tax that raises the same amount of money in the cigarette market.
The supply and demand curves for the book market are:
$$P = 17002 - Q_D$$
$$P = 1000 + Q_S$$
...and the supply and demand curves for the cigarette market are:
$$P = 20004 - 3Q_D$$
$$P = 4000 + Q_S$$