The power of a point source of sound and the distance at which the sound is heard are given below for four different cases. Rank cases A through D in order of increasing intensity. Indicate ties where appropriate.
Case A: $P=10 \mathrm{~W}, r=1 \mathrm{~m}$
Case B: $P=20 \mathrm{~W}, r=2 \mathrm{~m}$
Case C: $P=50 \mathrm{~W}, r=5 \mathrm{~m}$
Case D: $P=100 \mathrm{~W}, r=5 \mathrm{~m}$