Bertha, a business analyst, wants to analyze Shop Wise Inc., a software company. She wants to know how the company, supplying its products and services for over a decade, still maintains competitive advantage over other companies. She does the analysis simply by walking around the company and taking notes. She even tries out one of the company's software programs and finds it useful. This scenario illustrates the use of __________.

a	interviews
b	focus groups
c	archival data
d	observation