Figure and Table: An Indifference Curve Map

$51.($Table: Marginal Benefit from Additional Streetlights$).$ Suppose that the marginal cost of installing a streetlight is $$3.$ What is the socially optimal number of streellights in the neighborhood?

a$.1$

b$.2$

c$.3$

d$.4$

$52.($Table: Marginal Benefit from Additional Streetlights$).$ Suppose that the marginal cost of installing a streetlight is $$3.$ If Dave had to pay for streetlights on his own, how many streetlights would there be$?$

a$.0$

b$.1$

c$.2$

d$.3$