Two Water Waves Meet at the Same Point,one Having a Displacement

Multiple Choice

Two water waves meet at the same point,one having a displacement above equilibrium of 30 cm and the other having a displacement above equilibrium of 90 cm.At this moment,what is the resulting displacement above equilibrium?

A) 120 cm
B) 75 cm.
C) 60 cm
D) Information about the amplitudes needs to be given to find an answer.
E) 75 cm