If the velocity of sound in air is $320 \mathrm{~m} / \mathrm{s}$, then (maximum and minimum audible frequency are $20 \mathrm{~Hz}$ and $20000 \mathrm{~Hz}$, respectively), the maximum and minimum lengths of a closed pipe that would produce a just audible sound are
(A) $2.6 \mathrm{~m}$ and $3.6 \times 10^{-3} \mathrm{~m}$
(B) $4 \mathrm{~m}$ and $4.2 \times 10^{-3} \mathrm{~m}$
(C) $3 \mathrm{~m}$ and $3 \times 10^{-3} \mathrm{~m}$
(D) $4 \mathrm{~m}$ and $4 \times 10^{-3} \mathrm{~m}$