Which element is between “depths” and “vitae” in step IV?

Concepts for number arrangement: Numbers are arranged in ascending order from left to right. Concepts for word arrangement: Words are arranged in increasing number of vowels in the word from right to left. Input: rain 82 adieu 38 depths 64 automobile 52 vitae 46 Step I : 38 rain 82 adieu 64 automobile 52 vitae 46 depths Step II : 46 38 82 adieu 64 automobile 52 vitae depths rain Step III : 52 46 38 82 adieu 64 automobile depths rain vitae Step IV : 64 52 46 38 82 automobile depths rain vitae adieu Step V : 82 64 52 46 38 depths rain vitae adieu automobile And Step V is the last step of the above arrangement as the intended arrangement is obtained.