The algorithm in Figure 1 is designed to check if a room's ceiling height is valid (at least 3 metres) and calculate the clearance. It contains a logic error on line 11.

Figure 1

1  validMeasurement ← False
2  REPEAT
3      clearance ← 0
4      OUTPUT 'Enter floor height: '
5      floorHeight ← USERINPUT
6      OUTPUT 'Enter ceiling height: '
7      ceilingHeight ← USERINPUT
8      IF floorHeight ≥ ceilingHeight THEN
9          OUTPUT 'Floor height must be less than ceiling height'
10     ELSE
11         IF ceilingHeight ≥ 3 THEN
12             OUTPUT 'Ceiling height must be at least 3 metres'
13         ELSE
14             validMeasurement ← True
15         ENDIF
16     ENDIF
17 UNTIL validMeasurement = True
18 clearance ← ceilingHeight - floorHeight
19 OUTPUT clearance