A transverse wave along a chord is given by D$($x$,$t$)=0\mathrm{.}015$sin$(25$x$-1200$t$)$ where D and x are in meters and t is in

seconds. What is the speed of the wave?

$48($ m$)/($s$)$

$25($m$)/($s$)$

$0\mathrm{.}02($m$)/($s$)$

$12($m$)/($s$)$

$1200($ m$)/($s$)$