Assume that the ends of the bar have been kept at 100 degrees C for a long time. Then at some instant, call it t=0, the temperature at x=L is suddenly changed to 0 degrees C and kept at 0 degrees C, whereas the temperature at X=0 is kept at 100 degrees C. Find the temperature in the middle of the bar a t=1,2,3,10,50 seconds. First guess then calculate.