Please help me with the following practice questions. Clearly show the answer and explain how you got it so that I can better understand this class. Thank you!

Suppose identifiers in a programming language must begin with a letter followed by letters, digits or underscores. How many identifiers of length 3 are possible? 17,576 33,696 35,594 O 962 Among a group of 58 programmers, who know either Java or Python or both, 15 only know Java and 13 only know Python. What is the probability of randomly choosing a programmer who knows both languages? 15/58 15/29 13/58 13/28 In a group of 78 students, 19 are juniors and 23 seniors. What is the probability that a student is either a junior or senior? 19/76 23/76 4/13 7/13