Tafea_a: refers to the optimal solution with plane, boat, truck, and small drone as transportation modes

Tafea_b: refers to the optimal solution with plane, boat, truck, and large drone as transportation modes

Tafea_f: refers to the optimal solution with plane, boat, truck, small drone and large drone as transportation modes

Tafea_h: refers to the optimal solution with plane, boat, truck (no drones)