how long does it take to send out 100 bits?

100/2000 = 0.05 sec

How long does it takes to send out a single character of 8 bits?

8/2000 = 0.004 sec

How long does it take to send a file of 100000 characters?

As, single character is of 8 bits.So,

{8*100000}/2000 = 400 sec