A transverse wave on a cord is given by D$($x$,$t$)=0\mathrm{.}15$sin$(3\mathrm{.}0$x$19\mathrm{.}0$t$)$D$($x$,$t$)=0\mathrm{.}15$sin$(3\mathrm{.}0$x$19\mathrm{.}0$t$),$ where DD and xx are in meters$$and tt is in seconds. What is the period of this wave?