A wave on a string is described by $D(x,t)=(2\mathrm{.}8cm)sin[2(\frac{x}{7\mathrm{.}2m}+\frac{t}{0\mathrm{.}26s}+1)],$ where $x$ is in $m$ and $t$ is in $s.$

$1.$ What is the frequency?

$2.$ What is the wave number $?$

$3.$ At t$=0\mathrm{.}39$s$,$ what us the displacement of the string at x$=4\mathrm{.}2$m

Express answers in apporporiate units.