solve plz

only formulation please and if you can solution would be great as well

The Bill-of Materials for a wooden chair has two levels. The first level consists of the seat, the leg assembly and the back assembly. The second level for the leg assembly consists of two legs and a cross bar and the second level for the back assembly consists of 2 side rails, three back supports and a cross bar. Two options are viable. 1) Purchase all wooden parts from a subcontractor and perform only assembly operations in house. 2) make and assemble all parts in house. Assume a planning horizon of 12 months and that the required production quantity for finished chairs is dt in month t and the total monthly machining hours available is 160. Also assume that each leg and each cross bar takes 0.05 hours of machine time, and each side rail and each back support takes 0.1 hours of machine time. Finally, assume that the total in house assembly capacity (leg assembly + back assembly + final assembly) available per day is 20 chairs at most. Let Cij be the unit production cost of component j, Czj be the unit cost of purchasing component j from the subcontractor, Cz be the total unit assembly cost and C4 be the fixed investment cost of the machines, h be the holding cost per component per month. Formulate a production planning model to evaluate the optimal in-house production plan