David is answering the telephone during a radio broadcast fund drive. People phone in pledges of $5 or more per month. Experience has shown that 45% of the callers pledge more than $5 per month. What is the probability that on a given day the first caller to pledge over $5 per month is the fourth call of the day?

Now...the geometpdf(p,n) is for the probability of first success on trial number.

Is this the right DISTR key to use with my Ti-83??

It looks like this on the calculator:

geometpdf(.45,4) = .07486875

I used .45 as the p and the number 4 because they want the 4th caller to be the success. Let me know if I did this right.