An open organ pipe of length 0.85m is in unison with an identical pipe at 20∘C. The speed of sound in air varies with temperature according to v=332+0.6T (in m/s, T in ∘C). If the temperature of one pipe is raised to 30∘C while the other remains at 20∘C, calculate the time interval between successive amplitude maxima of the beats produced when both pipes sound their fundamental notes.
a) 0.14s
b) 0.28s
c) 0.57s
d) 0.20s