Sound Waves Frequency Calculation Help

[nubey1]

Homework Statement

A loudspeaker at the origin emits sound waves on a day when the speed of sound is 340 m/s. A crest of the wave simultaneously passes listeners at the coordinates (38m,0m) and (0m,29m). What are the lowest two possible frequencies of the sound?

Homework Equations

D(x,t)=Asin(kx-wt+$$\phi$$)
D(y,t)=Asin(kx-wt+$$\phi$$)

The Attempt at a Solution

I do not know where to start with this problem. I received some advice from the TA, but I am still confused.

 

[lanedance]

assume the wave eminates spherically from the speaker

the fact that they are different distances from the speaker means the listeners both hear different crests at the same time...

think about distances...

how apart are crests in the wave...

how far is each listener form the speaker...