Consider the following first-order dynamic system described by the differential equation:
3.5y(t) + y(t) = 2.5u(t) + d(t)

where y(t), u(t), and d(t) are respectively the output, manipulated input, and disturbance of the process in deviation variable form. The initial condition of the system is y(0) = 0.

Based on this information,
1. Create an M-file of MATLAB showing the code for solving the differential equation describing the given system. Make the code organized so that it is easily readable.