solve with excel / found the optimum solution

Q1) The property manager of a city government issues chairs, desks, and othe office furniture to city buildings from a centralized distribution center. Like most government agencies, it operates to minimize its costs of operations. In this distribution center, there are two types of standard office chairs, Model A and Model B. Model A is considerably heavier than Model B, and costs $20 per chair to transport to any city building; each model B costs $14 to transport. The distribution center has on hand 200 of A Model chairs, and 200 of B Model chairs. The requirements for shipments to each of the city's buildings are as follows: Building I needs at least 100 of A Building 2 needs at least 150 of B. Building 3 needs at least 100 chairs, but they can be of either type, mixed. Building 4 needs 40 chairs, but at least as many B as A. a) Formulate the problem. b) What is the optimum solution? Show all your work and state clear conclusion