A boat is travelling in a river with a speed of 10 m/s along the stream flowing with a speed of 2 m/s. From this boat, a sound transmitter is lowered into the river through a rigid support. The wavelength of the sound emitted from the transmitter inside the water is 14.45 mm. Assume that attenuation of sound in water and air is negligible. The frequency detected by a receiver kept inside the river downstream is fo and the transmitter and the receiver are now pulled up into air. The air is blowing with a speed 5 m/sec in the direction opposite the river stream the frequency of the sound detected by the receiver is f. (Temperature of the air and water = 20C; Density of river water = 10 kg/m; Bulk modulus of the water = 2.088 10 Pa; Gas constant R = 8.31J/mol-K; Mean molecular mass of air = 28.8x10-kg/mol; Cp/Cv for air = 1.4) Note: Boat velocity is with respect to ground & receiver is stationary w.r.t ground 18. The value of fo (KHZ) is_ 19. The value of f (KHZ) is_