w II. At an E-W-N-S interaction, the red-light time of E-W and N-S direction is to and t2, respectively, and to +t2=1 min in every 10 min. The car flow rate (number of cars passing in 1 min) in E-W and N-S direction is Q1 and Q2, respectively, and they are functions of t1 and te, or, Q1-Q (ti, tz), Q2=Q2(t1, tz). A design is looked for ( t) such that (Q1+Q2) takes a maximum value. Write this design problem into a math problem (8 pts). w II. At an E-W-N-S interaction, the red-light time of E-W and N-S direction is to and t2, respectively, and to +t2=1 min in every 10 min. The car flow rate (number of cars passing in 1 min) in E-W and N-S direction is Q1 and Q2, respectively, and they are functions of t1 and te, or, Q1-Q (ti, tz), Q2=Q2(t1, tz). A design is looked for ( t) such that (Q1+Q2) takes a maximum value. Write this design problem into a math problem (8 pts)