Please do you best try and explain it, thanks a lot!

Consider an economy with only two goods, delicious cinnamon rolls and comfy woolly sweaters. The leader of the country needs to know the average price for all goods. Which of these equa- tions is NOT an equation for the average price level (P)? (Country-wide production can be characterised with the Cobb-Douglas production function). A P = 1tu WN 1 -a Y C P = [1+ -]MC BP _ Itu W 1-a El -a (N ) -a DP = (1+/) MPL W