Question

Two point sources emit sound waves of 1.0-m wavelength. The sources, 2.0 m apart, as shown below, emit waves which are in phase with each other at the instant of emission. Where, along the line between the sources, are the waves out of phase with each other by pi radians?

I know that at the antinodes, the diffrence is pi radians and i got 0.5, 0.5, 1 and 1.25 for the position of antinodes. but the answer is x = 0.75 m, 1.25 m.

what am i doing wrong