Write the Excel binomial formula for each probability.
a. Three successes in 20 trials with a 30 percent chance of success.
b. Seven successes in 50 trials with a 10 percent chance of success.
c. Six or fewer successes in 80 trials with a 5 percent chance of success.
d. At least 30 successes in 120 trials with a 20 percent chance of success.