On street AB, three traffic lights are connected. Let i be the index of the ith traffic light and Ti is the waiting time behind the ith traffic light. On average the waiting time for both the ith traffic light is i minutes.

1) What is the appropriate probability distribution to model Ti

2) Find the probability that Ti is greater than 30 seconds

3) What is the probability model of T1+T2 if waiting times are independent(Specify parameter model)

4) What is the expectation and standard deviation of waiting time on street AB