A student has a​ one-dollar bill, a​ five-dollar bill, and a​ ten-dollar bill in a box. The student selects a bill from the box 40 times and selects the one dash dollar bill 13 times. What formula should be used to calculate the experimental​ probability? What is the experimental probability of selecting the one dash dollar ​bill? What is the theoretical probability of selecting the one dash dollar ​bill?