One end of a string is tied to the ceiling of a lift and a load is attached at the bottom end of the string. When the lift is moving upwards with an acceleration of 2.1 $\mathrm{ms}^{-2}$, the speed of the transverse wave at the lower end of the string is $88 \mathrm{~ms}^{-1}$. If the lift moves downwards with an acceleration of $1.9 \mathrm{~ms}^{-2}$, the speed of the transverse wave at the lower end of the string is $\left(g=10 \mathrm{~ms}^{-2}\right)$

Among the following statements, the correct statement for a wave is

A source and an observer move away from each other with same velocity of $10 \mathrm{~ms}^{-1}$ with respect to ground. If the observer finds the frequency of sound coming from the source as 1980 Hz , then actual frequency of the source is (speed of sound in air $=340 \mathrm{~ms}^{-1}$ )

A wave is given by $y=5 \times 10^{-3} \sin \left(12.5 \pi x-\frac{\pi}{2} t\right)$. Then its wavelength and time period are respectively ( $y$ and $x$ are in metres and $t$ is in seconds)