You could figure out the z-score for D equaling zero, and that's pretty straightforward. You could just say this z is equal to zero minus our mean of eight divided by our standard deviation of 10. So it's negative eight over 10, which is equal to negative 8 1⁄10. So you could look up a z-table and say, what is the total area under the curve below z is equal to negative 0.8? Another way you could do this is you could use a graphing calculator. I have a TI-84 here, where you have a normal cumulative distribution function. I'm gonna press second, vars, and that gets me to distribution.