A hydrogen filled balloon ascending at the rate of 18 kmph was drifted by wind. Its angle of elevation at 10th and 15th minutes were found to be $$60^\circ$$ and $$45^\circ$$ respectively. The wind speed (in whole numbers) during the last five minutes, approximately, is equal to

A

7 km/hr

B

11 km/hr

C

26 km/hr

D

33 km/hr