ເຄື່ອງຄິດໄລ່ທີ່ມາຂອງ Doppler

I want to calculate
Wave Velocity(v) = m/s
Wavelength Behind Source(λb) = m
New Frequency of Receding Source(f') = Hz
   
ເຄື່ອງຄິດໄລ່ທີ່ມາຂອງ Doppler