You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: aco2i8d.m
    path of file: ./repos/calfem-matlab/str_fl_int
    
    the code of the file until where you have to start completion: function [Ke,Me,fe]=aco2i8d(ex,ey,ep,eq)
% Ke=aco2i8d(ex,ey,ep)
% [Ke,fe]=aco2i8d(ex,ey,ep,eq)
%-----------------------------------------------------------
% PURPOSE
%  Compute element stiffness and mass  
%  matrix for 8 node isoparametric acoustic element
%
% INPUT:  ex = [x1 ... x8]    element coordinates
%         ey = [y1 ... y8]
%                             
%         ep = [t c raa ir]   thickness, speed of sound, 

    
function [Ke,Me,fe]=aco2i8d(ex,ey,ep,eq)
% Ke=aco2i8d(ex,ey,ep)
% [Ke,fe]=aco2i8d(ex,ey,ep,eq)
%-----------------------------------------------------------
% PURPOSE
%  Compute element stiffness and mass  
%  matrix for 8 node isoparametric acoustic element
%
% INPUT:  ex = [x1 ... x8]    element coordinates
%         ey = [y1 ... y8]
%                             
%         ep = [t c raa ir]   thickness, speed of sound, 
%                             density, integration rule
%
%         eq                  mass inflow per unit volume
%                             and time (second derivative)
%
% OUTPUT: Ke :  element stiffness matrix (8 x 8)
%         Me :  element mass matrix (8 x 8)
%         fe :  element load vector (8 x 1)
%-----------------------------------------------------------

% LAST MODIFIED: G Sandberg    1996-03-08
% Copyright (c)  Division of Structural Mechanics and
%                Department of Solid Mechanics.
%                Lund Institute of Technology
%-------------------------------------------------------------
%irk=2;irm=3; to be used if different 'ir' is used for the mass and stiffness

t=ep(1); c=ep(2); raa=ep(3); ir=ep(4); ngp=ir*ir;
  if nargin==3; eq=0 ; end