$24 \%$ adults favor the use of unmanned drones by police agencies. Twelve U.S. adults are randomly selected. Find the probability that the number of U.S. adults who favor the use of unmanned drones by police agencies is (a) exactly three, (b) at least four, (c) less than eight. (a) $P(3)=$ (Round to three decimal places as needed.)

Step 1 ：This problem is a binomial probability problem. The probability of success (favoring the use of unmanned drones) is 0.24, the number of trials is 12, and we want to find the probability of exactly 3 successes.

Step 2 ：The formula for binomial probability is: \(P(x) = C(n, x) * (p^x) * ((1-p)^(n-x))\), where \(C(n, x)\) is the number of combinations of n items taken x at a time, \(p\) is the probability of success, \(n\) is the number of trials, and \(x\) is the number of successes.

Step 3 ：Substituting the given values into the formula, we get \(P(3) = C(12, 3) * (0.24^3) * ((1-0.24)^(12-3))\).

Step 4 ：Calculating the above expression, we get \(P(3) = 0.2572638333177211\).

Step 5 ：Rounding to three decimal places as needed, we get \(P(3) = 0.257\).

Step 6 ：Final Answer: \(P(3) = \boxed{0.257}\)