Clarify depth in fluid force problem

With the original wording, it's not clear exactly how the plate is
submerged.  Is the top of the plate, the bottom, or maybe even the
middle of the plate at the given depth?

Based on the solution, it is the bottom of the plate that's submerged
to this depth, so we clarify that in the wording of the problem.

Author: d-torrance

OpenProblemLibrary/UMN/calculusStewartET/s_8_3_prob01.pg

@@ -54,7 +54,7 @@ $BBOLD 1. $EBOLD Find the hydrostatic pressure at \($dep\text{m}\). $BR
 Answer (in Newtons per sq. meter): \{ans_rule(20) \} $PAR
 $BBOLD 2. $EBOLD Find the hydrostatic force on a square steel plate with sides \($wid\text{m}\) placed horizontally. $BR
 Answer (in Newtons): \{ans_rule(20) \} $PAR
-$BBOLD 3. $EBOLD Find the hydrostatic force on a square steel plate with sides \($wid\text{m}\) placed vertically. $BR
+$BBOLD 3. $EBOLD Find the hydrostatic force on a square steel plate with sides \($wid\text{m}\) placed vertically so that the bottom is at \($dep\text{m}\). $BR
 Answer (in Newtons): \{ans_rule(20) \}
 $HR
 END_TEXT