A wave disturbance in a medium is described by $y(x, t)=0.02 \cos \left(50 \pi t+\frac{\pi}{2}\right) \cos (10 \pi x)$
where $x$ and $y$ are in meter and $t$ is in second. Then
(A) First node occurs at $x=0.15 \mathrm{~m}$
(B) First anti-node occurs at $x=0.3 \mathrm{~m}$
(C) The speed of interfering waves is $5.0 \mathrm{~m} / \mathrm{s}$
(D) The wavelength is $0.2 \mathrm{~m}$