A dealer's profit in units of $5,000 on a new automobile is a random variable X having density function

f(x,y) = 2(1-x) for -1 <= x <= 1

a) Find the vaiance in the dealer's profit.

b) Demonstrate that chebyshev's inequality holds for k = 2 with the density function above.

c) What is the probability that the profit exceeds $500?

a) E(2(1-x)) = -4

$\displaystyle \int-1,1 (-2x-1)f(x)dx$ What is f(x) in this problem?

b) How can I show that it holds true?

c) ???