I need just formulation. Just modelling. I dont need to cost amount. Just formulation or modelling part. Decision variables and constraints etc.

A local power company is considering increasing its generating capacity to meet expected demand over the next 5 years. Currently, the company has a generating capacity of 600 MW. As per the demand forecast, the minimum generating capacities required over the next 5 years are as follows: Year 1 2 3 4 5 670 760 890 1020 1180 Minimum capacity (MW) The company can increase its transmission capacity by purchasing five different types of generators: 20, 50, 80, 100, and 120 MW. The costs of acquiring, installing, and operating each of the five types of generators are summarized below: Acquiring and Generator Type (MW) Installation Cost/Unit" Operating Cost/Unit/Year 20 5.0 2.0 50 10.0 4.0 80 13.0 6.0 100 17.0 8.0 120 22.0 10.0 "In million dollars. Any number of generators (of any type) can be added in any year. However, once a generator is added, it must be operated in the future years as required. Formulate a mathematical programming model to determine the least cost expansion plan, for 5 years, while fulfilling all yearly demand