Sitting on the banks of the river, Aladdin and his friends see a group of sailors preparing their boat to sail south. Genie had never been to the south and this makes him interested in their sail and he wants to know where they were heading. Using his magical powers, he gathers everyone together and places a magical hat on some of the sailor’s head (i.e at least one person has a hat). The hat is magical as it can be seen by other people, but not by the wearer of the hat himself. The sailors find out about the hat and in order remove the hat, those ( and only those who have a hat) must dunk themselves underwater at exactly mid- night.
If ai number of sailors dunk their hats on i-th day, find the sum of `a_(i)` x i for all the days till all the hats are removed. If there are 50 men and 7 hats find the sum.

Options

A. 350
B. 49
C. 28
D. 7