The answer is 60. The lines surrounding the 60 mean absolute value. It doesn't do anything when the number is positive. Let's say if the number was [-60] then it would change to 60 because that is what absolute value does.
and are the amplitudes of the waves and , respectively. From the plot it's clear that both and are positive, but the maximum value of is evidently smaller than the maximum value of . So , making the answer B.