Your mother $($without glasses$)$ can see things clearly only if they are between $23\mathrm{.}0$ cm and $170$ cm from her eyes.

$($a$)$ If her glasses are to sit $2\mathrm{.}20$ cm from her eyes, determine the refracting power needed for glasses that will correct her myopia.

D

$($b$)$ Determine your mother's near point when wearing these glasses.

cm