What is the expanded form of the decimal 509.1? a) (5 x 100) + (9 x 10) + (1 x 1 10 ) b) (5 x 100) + (9 x 10) + (1 x 1 100 ) c) (5 x 100) + (0 x 10) + (9 x 1) + (1 x 1 10 ) d) (5 x 1000) + (9 x 100) + (1 x 10) + (1 x 1 10 )