If $a = 50(99)^{99} + 20(99)^{99}, \; b = 99^{100}$ and $c = 90(90)^{99}$, then which of the following expresses the correct ordering of $a, \; b$ and $c$.

Question

$\begin{array}{1 1} (a)\;a>b>c \\ (b)\; b > c>a \\ (c)\; b > a> c \\ (d)\; a > c>b \end{array}$