Task: Question Answering
Input (English): Problem: if ( 18 ^ a ) * 9 ^ ( 3 a – 1 ) = ( 2 ^ 4 ) ( 3 ^ b ) and a and b are positive integers , what is the value of a ? 
Options: a ) 22 , b ) 11 , c ) 9 , d ) 6 , e ) 4
Output (English): e