You may assume that this line already exists before your code: import numpy as np a) Write a line of code of code to create a NumPy array variable named x that contains the following values: 12, 9, 6, 3, 0, -3, 18, 20, 22, 24, 26, 28 Use ONLY NumPy's arange() and concatenate() function calls. Do NOT use array(). Hint: Perhaps you can do something twice and put the results together. b) Write a line of code using index slicing that extracts just the numbers 0, -3, 18, 20 from array x and assigns the result to a new variable named z. c) Write a line of code that sets only the values of x that are even to the number 0 by using conditional indexing. The final version of array x should contain: 0, 9, 0, 3, 0, -3, 0, 0, 0, 0, 0, 0