A spread footing supported on a sandy soil has been designed to support a certain column load with a factor of safety of 2.5 against bearing capacity failure. However, there is some uncertainty in both: the column load, P, and the friction angle, ?. Which one of the following would have the greatest impact on the actual factor of safety: An actual P that is twice the design value, or actual ? that is half the design value? Use bearing capacity computations with reasonably assumed values to demonstrate the reason of your response.