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: 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


[Q]: Problem: a football field is 7200 square yards . if 1200 pounds of fertilizer are spread evenly across the entire field , how many pounds of fertilizer were spread over an area of the field totaling 3600 square yards ? 
Options: a ) 450 , b ) 600 , c ) 750 , d ) 2400 , e ) 3200
[A]: b


[Q]: Problem: if the length of the longest chord of a certain circle is 18 , what is the radius of that certain circle ? 
Options: a ) 2.5 , b ) 9 , c ) 10 , d ) 15 , e ) 20
[A]:
b