pls give explanation. thanks

Homework 5B: Problem 12 Previous Problem Problem List Next Problem (9 points) A bag contains two red balls, one green ball, and six yellow balls. Balls are drawn from the bag one at a time at random without replacement until a yellow ball has been drawn, Let random variable R represent the number of red balls drawn. Complete the probability distribution function for R in the table below, putting the values of R in ascending order. R Pr(R) Enter your answers as whole numbers or fractions in lowest terms