total amount of space leased $($by adding a new lease and$/$or having an old lease expire$)$ at least once but not every month.

The space requirement and the leasing costs for the various leasing periods are as follows.

The objective is to minimize the total leasing cost for meeting the space requirements.

a$.$ Indicate why this is a cost$-$benefit$-$trade$-$off problem by identifying both the activities and the benefits being sought from these activities.

b$.$ Identify verbally the decisions to be made, the constraints on these decisions, and the overall measure of performance for the decisions.

c$.$ Convert these verbal descriptions of the constraints and the measure of performance into quantitative expressions in terms of the data and decisions.

use Solver to solve the model.

e$.$ Summarize the model in algebraic form.