Problem (3): A 0.4-cm-thick, 12-cm-high, and 18-cm-long circuit board houses 80 closely spaced logic chips on one side, each dissipating 0.04W. The board is impregnated with copper fillings and has an effective thermal conductivity of 30W/mK. All the heat generated in the chips is conducted across the circuit board and is dissipated from the back side of the board to a medium at 40C, with a heat transfer coefficient of 52W/m2K. (a) Determine the temperatures on the two sides of the circuit board. (b) Now a 0.2-cm-thick, 12-cm-high, and 18-cm-long aluminum plate (k=237W/mK) with 8642cm-long aluminum pin fins of diameter 0.25cm is attached to the back side of the circuit board with a 0.02-cm-thick epoxy adhesive (k=1.8W/mK). Determine the new temperatures on the two sides of the circuit board. [10 points]