Problem: in a rectangular coordinate system , what is the area of a rectangle whose vertices have the coordinates ( - 5 , 1 ) , ( 1 , 1 ) , ( 1 , - 4 ) and ( - 5 , - 4 ) ? 
Options: ['a ) 20', 'b ) 30', 'c ) 40', 'd ) 55', 'e ) 48']
b