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

Q: Problem: if 21 lines are drawn in a plane such that no two of them are parallel and no three are concurrent , then in how many points do they intersect ? 
Options: a ) 150 , b ) 170 , c ) 190 , d ) 210 , e ) 230

A: d
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Q: Problem: a 600 meter long train crosses a signal post in 15 seconds . how long will it take to cross a 3 kilometer long bridge , at the same speed ? 
Options: a ) 4 min , b ) 2 min , c ) 8 min , d ) 9 min , e ) 1.5 min

A: e
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Q: Problem: if the product of two numbers is 82500 and their h . c . f . is 55 , find their l . c . m . 
Options: a ) 2574 , b ) 2500 , c ) 1500 , d ) 1574 , e ) none of these

A:
c
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