Answer:
subsidies
Step-by-step explanation:
Subsidies refer to financial aid for some specific purpose and to some specific category as decided by the government. As for the instance the government can provide subsidy in the form of house to poor people in the country.
Now here the rich people can afford their own houses and that they can pay the taxes as well which are attached to the the houses, which provide extra benefit to the poor, as the government can provide the subsidy then more efficiently.
The positive externalities increase the benefits for every citizen.