Greedy algorithms

Bob is traveling from city $A$ to city $D$ via cities $B$ and $C$. There are several ways to get from one city to another, and travel costs are different for different mediums. The options are depicted below:

Bob wants to travel from city $A$ to city $D$ with the lowest possible cost. Please derive the optimal solution for Bob using the Greedy algorithm and write it below.

Please write your answer in this format: Bus, Train, Train