Find number of words made using letters of word 'EQUATION' if order of vowels do not change.

My attempt:- since we do not have to change the order of the vowels hence, 
 \_E\_U\_A\_I\_O\_
we have $6$ places to fill the remaining letters. Therefore total number of cases $= C(6,3) \times 3! + 6 \times 3!= 156$ 
But the answer is $336$.