The linear density of a string is $1\mathrm{.}210$ kg$/$m$.$ A transverse wave on the string is described by the equation y $=(0\mathrm{.}015$ m$)$ sin$[(2\mathrm{.}5$ m $)$x $+(39$ s $)$t$]$ What are $($a$)$ the wave speed and $($b$)$ the tension in the string?