Explanation:

- A boat travels upstream for 14 km in 84 minutes.

- Speed of the stream is given as 6 km/h.

- 84 minutes is equal to 1.4 hours (since 84/60 = 1.4).

- Speed upstream is calculated as distance/time which is 14 km / 1.4 hours = 10 km/h.

- Let’s denote the speed of the boat in still water as 'b' km/h.

- We know that the speed upstream is 'b - 6' km/h (since the stream opposes the movement).

- By setting up the equation b - 6 = 10, we solve for 'b', which gives b = 16 km/h.

- The options available are: 16 km/h, 22 km/h, 18 km/h, 12 km/h, and none of the above.

- The correct answer is option 1, 16 km/h.