$1.(20$pts$)$ Problem $16\mathrm{.}13($Knight$)$

The displacement of a wave traveling in the positive$$x$$direction$$is$$D$($x$,$t$)=(3\mathrm{.}5$cm$)$sin$(2\mathrm{.}7$x$122$t$),$where$$x$$is in$$m$$and$$t$$is in$$s$.$

a$)$ What is the frequency of this wave?

b$)$ What is the wavelength of this wave?

c$)$ What is the speed of this wave?