A simulation that involves drawing two marbles out of a bag has already been done and the data from the simulation is provided for you in a file called marbles$-$simulation.csv$.$ The simulation was drawing from a bag that had $3$ red marbles, $5$ blue marbles, and $10$ white marbles. The results of the simulation are stored in DataFrame with columns draw$1$ and draw$2.$

The values in the columns draw$1$ and draw$2$ are integers that represent a color. Specifically:

$1-3$ represents red,

$4-8$ represents blue, and

$9-18$ represents white

The results of this simulation are provided to you in a DataFrame named df$.$ Using df$,$ write the Python code to calculate the estimated probability of drawing exactly one red marble and one white marble and store that probability in a variable named prob. Make sure to return your variable at the end.