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: if a is a positive integer , and if the units digit of a ^ 2 is 9 and the units digit of ( a + 1 ) ^ 2 is 4 , what is the units x digit of ( a + 2 ) ^ 2 ? 
Options: a ) 1 , b ) 3 , c ) 5 , d ) 6 , e ) c . 14
a

Problem: if z is not equal to zero , and z = 6 zs − 9 s 2 − − − − − − − − √ z = 6 zs − 9 s 2 , then z equals : 
Options: a ) s , b ) 3 s , c ) 4 s , d ) - 3 s , e ) - 4 s
b

Problem: 80 + 5 * 12 / ( 180 / 3 ) = ? 
Options: a ) 23 , b ) 78 , c ) 27 , d ) 61 , e ) 81

e