Heidleman industries is considering two types of materails for roofing its warehouses. epdm is an elastomeric polymer synthesized from ethylene, propylene, and a small amount of diene monomer, compounded with carbon black processing oils and various cross-linking and stabilizing agents. the 75 mil thickness will cost $4.10 per square foot and will last for 25 years. a thin sheet aluminum roof will cost $6.00 per square foot, but it will last for 50 years. using an interest rate of 5% per year, calculate the annual worth per square foot for the polymer and aluminum roof.

The business cycle is the periodic but irregular up-and-down movement in economic activity, measured by fluctuations in real gross domestic product (gdp) and other macroeconomic variables. a business cycle is typically characterized by four phases—recession, recovery, growth, and decline—that repeat themselves over time. economists note, however, that complete business cycles vary in length. the duration of business cycles can be anywhere from about two to twelve years, with most cycles averaging six years in length. some business analysts use the business cycle model and terminology to study and explain fluctuations in business inventory and other individual elements of corporate operations. but the term "business cycle" is still primarily associated with larger (industry-wide, regional, national, or even international) business trends.