The joint density function of the logarithm of the two random variables [math]X[/math] and [math]Y[/math] equals [math]f(x,y)[/math]. Which of the following expressions represent the joint density function of [math]X[/math] and [math]Y[/math]?

1. [math]y^{-1}x^{-1}f(\ln(x),\ln(y))[/math]
2. [math]f(\ln(x),\ln(y))[/math]
3. [math]y^{-1}x^{-1}f(x,y)[/math]
4. [math]e^x e^yf(e^x,e^y)[/math]
5. [math]x^{-1}f(\ln(x),x) + y^{-1}f(x,\ln(y))[/math]