Some airplanes have two identical engines. A person is standing 50.0 m away from an airplane with two engines and the pilot starts the first engine. The person hears a sound with an intensity of 3.16 W/m2
 
a. What is the sound level (in dB) the person hears when the pilot starts the second engine?
b. How far away does a person need to be in order for the person to hear a sound level of 65.0 dB?