On the surface of lake when the atmospheric temperature is $-15^{\circ} \mathrm{C}, 1.5 \mathrm{~cm}$ thick layer of ice is formed in $20 \mathrm{~min}$, time taken to change its thickness from $1.5 \mathrm{~cm}$ to $3 \mathrm{~cm}$ will be
(A) $20 \mathrm{~min}$
(B) less than $20 \mathrm{~min}$
(C) greater than $40 \mathrm{~min}$
(D) less than $40 \mathrm{~min}$ and greater than $20 \mathrm{~min}$