need help answering calculus and probability statistics questions - no lengthy explanation needed thanks

Question 2 Consider a familyr that has 4 children. Assume that Pr{kid is a. boy) = Pr{kid is a girl} = 1/2, and that the genders of the 4 kids are independent. What is 1e probability that all 4 kids are boys given that we know at least 3 of them are boys? 0 1f16 O 1:3 0 lf O 1,\"! 0 1:2