In this task, you need to provide the correct option for a given problem from the provided options.

Problem: a certain hobby shop sold model cars for $ 5.00 each and model trains for $ 8.00 each . if a customer purchased both cars and trains from the store for a total of $ 31.00 , what total number of cars and trains did the customer purchase ?
Options: a ) 3 , b ) 4 , c ) 5 , d ) 6 , e ) 7
c

Problem: the duplicate ratio of 6 : 4 is ?
Options: a ) 1 : 2 , b ) 9 : 4 , c ) 1 : 8 , d ) 1 : 18 , e ) 1 : 13
b

Problem: a certain music store stocks 800 cellos and 600 violas . of these instruments , there are 110 cello - viola pairs , such that a cello and a viola were both made with wood from the same tree ( each tree can make at most one viola and one cello , so there are no pairs other than these 90 ) . if one viola and one cello are chosen at random , what is the probability that the two instruments are made with wood from the same tree ?
Options: a ) 11 / 48,000 , b ) 1 / 8,100 , c ) 3 / 1,600 , d ) 1 / 90 , e ) 2 / 45
a