(c)
$I_{1} = \int_{1 - k}^{k}{xf\left\{ x(1 - x) \right\} dx}$
$= \int_{1 - k}^{k}{(1 - x)f\left\lbrack (1 - x)\left\{ 1 - (1 - x) \right\} \right\rbrack dx(putx = 1 - x)}$
$= \int_{1 - k}^{k}{(1 - x)f\left\{ x(1 - x) \right\} dx}$
$= \int_{1 - k}^{k}{f\left\{ x(1 - x) \right\} dx - \int_{1 - k}^{k}{xf\left\{ x(1 - x) \right\} dx}}$
$= I_{2} - I_{1}$
$\therefore 2I_{1} = I_{2}$
$\Rightarrow \ \ \frac{I_{1}}{I_{2}} = \frac{1}{2}$