27% of all college students major in STEM (Science, Technology, Engineering, and Math). If 39 college students are randomly selected, find the probability that a. Exactly 9 of them major in STEM.  b. At most 10 of them major in STEM.  c. At least 11 of them major in STEM.

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From the given information,

Consider, X be the random variable that shows the major in STEM which follows binomial distribution.

That is, 

$$\begin{gathered} X~bin\left(n=39,p=0.27\right) \\ f\left(x\right)=\left(39 \\ x\right)0.{27}^x\times {\left(1-0.27\right)}^{39-x},x=0,1,2,,,,,,,, \end{gathered}$$