250 students in a high school senior class are surveyed about what majors they intend to declare in college. Of the 250 students, 100 plan to major in mathematics, 80 plan to major in computer science and 20 plan to pursue a double major in mathematics and computer science. Let M be the even that a randomly selected student plans to major in mathematics and C be the event that a randomly selected student plans to major in computer science.

What is P(M), the probability that a student plans to major in mathematics?
What is P(C), the probability that a student plans to major in computer science?
What is P(M and C), the probability that a student decided to major in mathematics and computer science?
What is P(M or C), the probability that a student has chosen to major in mathematics or computer science?