Express each number in standard form.
a) 1 X 10^3 + 0 X 10^2 + 4 X 10 + 9 X 1
b) 4 X 10^4 + 3 X 10^3 + 8 X 10^2 + 7 X 10 + 0 X 1
c) 8 X 10^6 + 1 X 10^5 + 5 X 1