From annual data for 1972-1979, William Nordhaus estimated the following model to explain the OPEC's oil price behavior (standard errors in parentheses). Yt= 0.3X1t + 5.22X2t se= (0.03) (0.50) Where Y= difference between current and previous year's price (dollars per barrel) X1= difference between current year's spot price and OPEC's price in the previous year. X2= 1 for 1974 and 0 otherwise. Interpret this result and show the results graphically. What do these results suggest about OPEC's monopoly power?