Solving linear system of equations Ax=b enters into many scientific applications. In this paper, we consider a special kind of linear systems, the matrix A is an equivariant matrix with respect to a finite group of permutations.

As the work force ages and workers retirement age increases, the number of workers suffering from Work-related Musculoskeletal Disorders (WMSDs) has increased. In a recent study, the U.S Bureau of Labor reported that 6.9% of all WMSDs affected shoulders. Electricians, carpenters, and related construction crafts appear to experience higher incidence of these injuries due the nature of their work that require them often to use Awkward shoulder postures.

Much of the developed world’s construction workforce is increasing in average age, and yet construction workers typically retire well before they reach the age of sixty. One reason is that their bodies are worn out because of the nature of the work. We therefore face the challenge of both reducing their physical stress and increasing their productive work life, if we wish to avert an economic and social crunch given the demographic trends towards an aging population in most developed countries.