In a family of five persons A, B, C, D and E each and everyone loves one another very much. Their birthdays are in different months and on different dates. A remembers that his birthday is between 25th and 30th, of B it is between 20th and 25th , of C it is between 10th and 20th , of D it is between 5th and 10th and of E it is between 1st to 5th of the month, the sum of the date of birth is defined as the addition of the date and the month, for example 12th January will be written as 12/1 and will add to a sum of date of 13. (Between 25th and 30th includes both 25 and 30)
What may be the minimum average of their sum of the dates of births?