Two loudspeakers M and WN are located 20 m apart and emit sound at frequencies 118 Hz and 121 Hz, respectively. A caris initially at a point P , 1800 m away from the midpoint Q
of the line MN and moves towards @ constantly at 60 km/hr along the perpendicular bisector of MN. It crosses Q and eventually reaches a point R, 1800 m away from Q. Let v(t) represent the beat frequency measured by a person sitting in the car at time t. Let $$V_P, V_Q$$ and $$V_R$$ be the beat frequencies measured at locations P, Q and R, respectively. The speed of sound in air is 330 ms$$^{-1}$$ Which of the following statement(s) is(are) true regarding the sound heard bythe person?