The tension in a string is $20\mathrm{.}9$ N$,$ and its linear density is $1\mathrm{.}23$ kg$/$m$.$ A wave on the string travels toward the $$x direction; it has an amplitude of $3\mathrm{.}47$ cm and a frequency of $10\mathrm{.}4$ Hz$.$ What are the $($a$)$ speed and $($b$)$ wavelength of the wave? $($c$)$ Write down a mathematical expression $($like Equation $16\mathrm{.}3$ or $16\mathrm{.}4)$ for the wave, substituting numbers for the variables A$,$ f$,$ and $.$