There are two water tanks, A and B; A is much smaller than B. While tank A…

There are two water tanks, A and B; A is much smaller than B. While tank A fills at the rate of one litre every hour, tank B fills as 10, 20, 40, 80, 160, ... litres (at the end of the first hour B has 10 litres, at the end of the second hour it has 20 litres, and so on — the volume in B doubles every hour). If tank B is 1/16 full after 17 hours, what is the total duration required to fill it completely?