Round answer to 4 decimal places

Determine the probability of guessing at least 11 questions correct on an exam that contains 15 multiple choice questions, where the chance of guessing a question correct is .5, round to at least 4 decimals in all of your calculations. Hint: This is a Binomial distribution (please see lecture 5.2 Example of marble for the reason). Let X=number of chance of guessing a question correct out of 15, we are asking for P(X>=11), with P=0.5 and n=15