The correct answer is 99.06 .
Since we know that,
1 ft = 12 inches, (1ft)3 = (12)3inches3
& 1 inch = 2.54 cm , (1 inch)3 = (2.54)3cm3
& 1 cm3 = 1ml,
&(1 ml)/1000 = 1L, so (1cm3)/1000 = 1L.
& 1 min. = 60 sec.
Now, 1ft3 = (12)3x(2.54)3/(1000) L
and 1 min = 60 sec
So, 1ft3/min = (12)^3x(2.54)^3/(1000)x(60) L/s
Hence 210 ft3/min = 210x(12^)3x(2.54)^3/(1000)x(60).
= 99.06.
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