Modelling and Programming for Inventory Routing Problem

It's more or less of an inventory routing problem(IRP). The context is that we have 1 depot and 7 metal factories which are producing metal waste. The production rates of producing waste are P(i) (tons/hour) with i=1,2..7. The initial inventory levels of the 7 factories at T=0 are I(i) (tons) with i=1,2..7. Maximum level of inventory of 7 factories are the same called Imax. We have 2 trucks which can recycle waste with a recycling rate as Rec(tons/hour). We also have the time of travelling from i to j, included depot, which is a matrix 8 by 8. The problem is that we have to find the optimal routes of the 2 trucks to 7 factories in 5 days (8 hours/day only) and the sequence of factory visitted by each trucks, build the mathematical model to solve general cases and apply it with numerical instance (as mentioned above, very small number of factory and truck). Ps: after each day ( 8 working hours), trucks have to be at the depot for the next day. Also, Inventory level of any factory can not reach the maximum inventory level which is Imax. When the truck arrive at one factory, it can start recycling the waste, while, at the same time, that factory is still producing more waste. There is no need to recycling 100% the waste at a certain factory, the problem is more satisfying the maximum inventory level of the next factories. Please contact me via this email if you want to help this problem. vuongbuiviet@[login to view URL]