Whom Would You Trust as Most Reliable? Discuss the Credibility

Essay

Whom would you trust as most reliable? Discuss the credibility and authority of each individual or group listed with regard to the following issue:
You are thinking of insulating your attic and need advice relative to how much insulation you should install.
a. a company that sells insulation but does not install it
b. a company that sells and installs insulation
c. an energy consultant from your local gas and electric company
d. Consumer Reports
e. a friend who has recently had his attic insulated