Count and list cells that represent x% of the sum of a range (pareto)

A list of values are in column B (with names in column A). I need to:

1. count the minimum number of cells whose sum represent at least 75% of the values in column A

2. list the names the met the criteria above

For example, if column B contains

201540105

... then the answer should be 3 (representing values 40, 20 and 15).

No VB, and if possible no ArrayFormulas.