Create a subroutine to solve a 3 Times 3 system of linear equations (using matrix inversion (by showing that A is non-singular using MDETERM) or Solver- choose one of the two methods). Please describe in detail (i.e. with comments) your code. Confirm that your subroutine is working by solving the system from HW 9 (Q1). x+2y+3z=1 x-2z=0 2x+y=1.25 Create a subroutine for numerical integration of given data using the trapezoidal rule. Use the data from HW9 (Q2) to check the subroutine (estimate the total amount of water which flowed out of the lake from time 0 to time 9h)