A periodic transverse wave is established on a string such that there are exactly two cycles traveling along a $3\mathrm{.}0-$m section of the string. The crests move at $20\mathrm{.}0\frac{m}{s}.$

What is the shortest horizontal distance from a crest to a point of zero acceleration?

$0\mathrm{.}75$ m

$6\mathrm{.}0$ m

$3\mathrm{.}0$ m

$1\mathrm{.}5$ m

$0\mathrm{.}38$ m