The pattern of displacement nodes $\backslash ($ N $\backslash )$ and antinodes $\backslash ($ A $\backslash )$ in a pipe is NANANANANA when the standing$-$wave frequency is $1670$ Hz $.$ The pipe contains air at $\backslash (20^\{\backslash$circ$\}\backslash$mathrm$\{$C$\}\backslash ).$ The speed of sound in air is $\backslash (344\backslash$mathrm$\{$~m$\}/\backslash$mathrm$\{$s$\}\backslash ).$

Part A

Is it an open or a closed $($stopped$)$ pipe?

It is a closed pipe.

It is an open pipe.

It cannot be determined.

Part B

Which harmonic is this?

This is fourth harmonic.

This is fifth harmonic.

This is seventh harmonic.

This is ninth harmonic.