A wave is represented by the equation $Y=7 \sin \left(7 \pi t-0.04 \pi x+\frac{\pi}{3}\right) \quad x$ is in meters and $t$ is in seconds. The speed of the wave is
(a) $175 \mathrm{~m} / \mathrm{sec}$
(b) $49 \pi \mathrm{m} / \mathrm{s}$
(c) $\frac{49}{\pi} \mathrm{m} / \mathrm{s}$
(d) $0.28 \mathrm{\pim} / \mathrm{s}$