Constraint (1) is the capacity constraint while (2) and (3) ensure the city will be visited once and only once.
Constraints (4) and (5) ensure that each truck has the same number of complete routes (i.e., truck leaves and returns
to the plant) as the sub-tours assigned to it for complete delivery. Constraint (6) is the connection constraint for each
sub-tour and (7) is the sub-tour elimination constraint. Constraints (8), (9) and (10) restrict each vehicle to be of only
one type and enforce this on the route-defining variables. Constraint (11) ensures that a delivery is finished before
the product expires and (12) forces every delivery to be completed before the time horizon ends. Constraint (13) and
(14) ensure that a delivery cannot begin before the product is ready and that the delivery truck cannot start a new trip
until it has returned to the plant from its previous trip. Constraint (15) forces production in the sequence of delivery
and forbids preemption. Constraint (16) restricts the plant to produce for one trip at any given time period and (17)
ensures the plant producing with fixed productivity. Constraint (18) and (19) together ensure the plant continues to
produce one batch until the entire quantity required for a trip is completed. Constraint (20) prevents a vehicle from
cycling