$7.$ Helium$-$neon laser light $(2=6\mathrm{.}33$ x $10$~$\text{'}$ m$)$ is sent through a $0\mathrm{.}30$ mm$-$wide single slit. What is the width

of the central maximum on a screen $1\mathrm{.}0$ m from the slit? a$.$ b$.$

$2\mathrm{.}0$ cm

$4\mathrm{.}2$ mm

$1\mathrm{.}1$ cm

d$.2\mathrm{.}0$ mm

$0\mathrm{.}70$ mm