You want a new cell phone. which of these sources would be the most dependable?

a. you read everything the phone maker says about its phones.
b. you research "cell phone reviews" and pay a lot of attention to comments from people who don't have anything to do with the cell phone manufacturer.
c. you only talk to users of that type of cell phone.
d. you read the fine print of the advertising on the cell phone.

David consumes two things: gasoline (g) and bread (b). david's utility function is u(g, b) = 10g^0.25 b^0.75. use the lagrange technique to solve for david's optimal choices of gasoline and bread as a function of the price of gasoline, p_g, the price of bread, p_b, and his income m. with recent decrease in the price of gasoline (maybe due to external shock such as shale gas production) does david increase his consumption of gasoline? for david, how does partial differential g/partial differential p_g depend on his income m? that is, how does david's change in gasoline consumption due to an increase in the price of gasoline depend on his income level? to answer these questions, find the cross-partial derivative, |partial differential^2 g/partial differential m partial differential p_g.