B 
Lee has $1$ red cube, $1$ yellow cube, $2$ blue cubes and $3$ green cubes. How many ways are there for Lee to arrange his cubes in a row if cubes of the same color is indistinguishable? 
Options:
(a) $$210$$ 
(b) $$420$$ 
(c) $$630$$ 
(d) $$840$$ 
(e) $$1050$$ 