What is the sum of all the digits of the number which is 4th smallest in step III?

All the numbers given in input are arranged in each step (in ascending order from left) after removing non-prime digits from it. One number is arranged in each step and every new number is placed at the left end after shifting previous numbers one place towards right. Input: 74936     58967    49772     83529      36947    66723 Step I: 37         74936     58967    49772       83529    66723 Step II: 772        37          74936     58967        83529    66723 Step III: 57        772           37         74936        83529    66723 Step IV: 723       57           772            37          74936    83529    StepV:73           723           57          772             37         83529    Step VI: 352        73          723           57            772            37