At night the pupils of a certain woman’s eyes are 8 mm in diameter.

(a) How many kilometers away from a car facing her will the woman be able to distinguish its headlights from each other? 

(b) What would the distance be if her pupils were 4 mm in diameter (say at twilight)? Assume that the headlights are 1.5 m apart, that the average wavelength of their light is 600 nm, and that her eyes attain half their theoretical resolving power.