An isolated three-phase traffic signal is designed by Webster's method. The critical flow ratios for three phases are $0.20,0.30,$ and 0.25 respectively, and lost time per phase is 4 seconds. The optimum cycle length (in seconds) is
An isolated three-phase traffic signal is designed by Webster's method. The critical flow ratios for three phases are $0.20,0.30,$ and 0.25 respectively, and lost time per phase is 4 seconds. The optimum cycle length (in seconds) is