Everyone

I have stuck in the problem of 2D conduction problem by using matlab, here is the following question:

Consider a long bar of square cross section (1.0 m to the side) and of thermal conductivity 2 W/m.K. Three of these sides are maintained at a uniform temperature of 300°C. The fourth side is exposed to a fluid at 100°C for which the convection heat transfer coefficient is 10 W/m2.K.

a)Using an appropriate numerical technique with a grid spacing of 0.2m, determine the midpoint temperature and heat transfer rate between the bar and the fluid per unit length of the bar.
b)Reducing the grid spacing by a factor of 2, determine the midpoint temperature and heat transfer rate. Plot the corresponding temperature distribution across the surface exposed to the fluid. Also, plot the 200 and 250°C isotherms.

Hopefully that anyone can give me some tips to do it. Thanks.