Check the picture below.
so the lateral area will be just the area of the sides, namely excluding the bases at top and bottom, thus

10%of 710 is 71
now we have 710-71=639
Less than greater than equal Too
The answer is B
15 L of pure water must be mixed with 10 L of a 25% acid solution to reduce it to a 10% acid solution
-20+14m=10m+16
-10m. -10m
-20+4m=16
+20. +20
4m=36
/4. /4
m=9