Task: Question Answering
Input (English): Problem: in the coordinate plane , line a has a slope of - 1 and an x - intercept of 1 . line b has a slope of 3 and a y - intercept of - 3 . if the two lines intersect at the point ( a , b ) , what is the sum a + b ? 
Options: a ) 0 , b ) 1 , c ) 2 , d ) 3 , e ) 4
Output (English): b