If the product of an even and an odd number is $$840={2^{3}}\times105$$, then the largest possible value of the odd number is $$105$$. 
If the product of an even number and an odd number is $$840$$, what is the largest possible value of this odd number? 

[a] $$21$$ 
[b] $$35$$ 
[c] $$105$$ 
[d] $$420$$ 