Given the WPO regression equation:

WPO= -2.3% + (.64) (S&P500)

Calculate the predicted value of WPO excess returns if forecasted S&P returns are 10%

Answer:

WPO = -2.3% + (.64) (10%) = 4.1%

How does this equal 4.1%? I get -2.236% so I’m not sure what I am doing wrong.