In this task, you need to answer the given multiple-choice question on geometry. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Q: Problem: the product of the squares of two positive integers is 9 . how many pairs of positive integers satisfy this condition ? 
Options: a ) 0 , b ) 1 , c ) 2 , d ) 3 , e ) 4

A: b
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Q: Problem: in an electric circuit , two resistors with resistances 3 ohm and 5 ohm are connected in parallel . in this case , if r is the combined resistance of these two resistors , then the reciprocal of r is equal to the sum of the reciprocals of two resistors . what is the value ? 
Options: ['a ) 15 ohms', 'b ) 15 / 8 ohms', 'c ) 1 / 8 ohms', 'd ) 8 / 15 ohms', 'e ) 8 ohms']

A: b
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Q: Problem: three walls have wallpaper covering a combined area of 300 square meters . by overlapping the wallpaper to cover a wall with an area of 180 square meters , the area that is covered by exactly two layers of wallpaper is 30 square meters . what is the area that is covered with three layers of wallpaper ? 
Options: a ) 5 square meters , b ) 36 square meters , c ) 42 square meters , d ) 45 square meters , e ) 120 square meters

A:
d
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