Can some help with these bat and insect flying problems?

Can some help with these bat and insect flying problems? Thank you.

12)  A bat (at rest) uses high frequency sound waves to "see." Assume the sound waves have frequency of 40,000Hz and move with a speed of 343m/s in air. What is the wavelength of this sound?

 2.3 mm

 4.2 mm

 5.7 mm

 7.0 mm

 8.6 mm

13)  The bat "sees" an insect by detecting it with its sound waves. If the sound takes .3 s total time to travel to the insect and then return to the bat after they bounce off the insect, how far away is the insect?

 46.9 m

 51.5 m

 60.2 m

 78.1 m

 106.3 m

14)  If the sound waves return at a frequency of 39,000Hz what direction is the insect moving?

 a. away from the bat

 b. toward the bat

c. it is not moving!

15)  How fast is the insect moving?

 a. 1.80 m/s

b.  2.55 m/s

 c. 3.81 m/s

d.  4.34 m/s

e.  5.67 m/s