Assist with HW questions

1. It is known that all items produced by a certain machine will be defective with a probability of .1, independently of each other.What is the probability that in a sample of twenty items, that exactly two will be defective? (assume binomial distribution)
2. It is known that all items produced by a certain machine will be defective with a probability of .1, independently of each other. What is the probability that in a sample of twenty items, that at most onewill be defective? (assume binomial distribution)
3. A Walnut processing facility clears an area around the drying sheds to allow hawks to attack walnut poaching squirrels.The squirrels can cover the distance from the trees to the drying shed with in a mean time of 38 seconds, and a standard deviation of 2.5 seconds (assumes normal distribution). What is the probability that a randomly selected squirrel will cover the distance in less 33 seconds (closest answer)?
4. A Walnut processing facility clears an area around the drying sheds to allow hawks to attack walnut poaching squirrels.The squirrels can cover the distance from the trees to the drying shed with in a mean time of 38 seconds, and a standard deviation of 2.5 seconds (assumes normal distribution). What is the probability that a randomly selected squirrel will cover the distance between 33 to 35 seconds?