(a) Given,

Speed of sound in air (V_{a}) = 340 m s^{-1}

Speed of sound in water (V_{w}) = 1360 m s^{-1}

Distance (d) = 1700 m

t = ?

V = Distance\over Time

Substituting the values for air, we get,

340 = 1700\over t

⇒ t = 1700\over 340 = 5 s

Therefore, **the time taken by sound to travel in air = 5 s**

(ii) Substituting the values for water, we get,

1360 = 1700\over t

⇒ t = 1700\over 1360 = 1.25 s

**the time taken by sound to travel in air = 1.25 s**