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

Problem: the unit digit in the product ( 891 * 781 * 912 * 463 ) is : 
Options: a ) 2 , b ) 5 , c ) 6 , d ) 8 , e ) 10
c

Problem: if | 5 x - 5 | = 150 , what is the sum of all the possible values of x ? 
Options: a ) 2 , b ) - 2 , c ) 6 , d ) - 3 , e ) 5
a

Problem: 3 - twentieths of the members of a social club are retirees who are also bridge players , 5 - twentieths of the members are retirees , and one - half of the members are bridge players . if 120 of the members are neither retirees nor bridge players , what is the total number of members in the social club ? 
Options: a ) 240 , b ) 300 , c ) 200 , d ) 400 , e ) 480

c