The stata file airelinecosts.dta contains data on indexes of variable costs (variablecost), output (seatmiles), prices of labor (pricelabor), materials (pricematerials), and fuel cost (pricefuel) for 23 airlines (name) for a maximum period of 13 years (years) from 1971 - 1986. The dataset contains 286 observations. If the production function is Cobb-Douglas, one can show that the variable cost function is of the form

log c=+ ylog y+ Mlog PM+ Llog PL+ Flog PF ,

where c denotes variable cost, y denotes output, and Pj denotes the price of input j.

1. Estimate the Cobb-Douglas cost function. Interpret the coefficients (discuss the sign, significance, and relative magnitude of each slope coefficient).