4. (a) A steel beam is 12 m long when installed at 32 C. Determine how much does its length change when it changes temperature from -23 C to 55 C. For steel = 1.1 105 C. [PHYS0030 MID-TERM EXAMINATION, 4/10/2021, 1430 - 1630 HRS (UTC +8 HOURS); 4(a)] (4 marks) (CLO2:PLO1:C3) (b) Two insulated rods, of thickness X and X2 and cross-section A are in thermal contact. Their non-contacting ends are at temperatures and 02, respectively. Assuming that the thermal conductivities for both materials as k and k2 respectively, determine the temperature at the interface between the two slabs. Leave your answers in terms of k, k2, 01, 02, X1, and X2. [PHYS0030 MID-TERM EXAMINATION, 4/10/2021, 1430 - 1630 HRS (UTC+8 HOURS); 4(b)] (6 marks) (CLO2:PLO1:C3)