Write a method that accepts an array containing 4 integer values representing a 2 by 2 matrix. Your method returns the determinate of that matrix. If the integers in the array are {a, b, c, d} they represent a square matrix in the form: a is the upper-left corner, b is the upper-right corner, c is the lower-left corner, and d is the lower-right corner. The determinate of that matrix is a*d-c*b. Look at the test data for further examples.