Answer
(a) $41.7diopters$
(b) increases
Work Step by Step
(a) We can find the refractive power as
$Refractive \space power=\frac{1}{f}=\frac{1}{d_{\circ}}+\frac{1}{d_i}$
We plug in the known values to obtain:
$Refractive \space power=\frac{1}{\infty}+\frac{1}{0.0240}$
$Refractive \space power=41.7diopters$
(b) As the distance $d_{\circ}$ decreases when we focus on the book, the refractive power will increase because refractive power and distance $d_{\circ}$ are inversely proportional.
