A Heat-Conducting Rod, 0 $0.70 \mathrm {~m}$ Long Both Sections Have a Cross-Sectional Area Of in Insulation

Multiple Choice

A heat-conducting rod, 0.90 m long and wrapped in insulation, is made of an aluminum section that is 0.20 m long and a copper section that is $0.70 \mathrm {~m}$ long. Both sections have a cross-sectional area of $0.00040 \mathrm {~m} ^ { 2 }$ The aluminum end and the copper end are maintained at temperatures of $30 ^ { \circ } \mathrm { C }$ and $230 ^ { \circ } \mathrm { C }$ respectively. The thermal conductivities of aluminum and copper are 205 W/m ∙ K (aluminum) and 385 W/m ∙ K (copper) . What is the temperature of the aluminum-copper junction in the rod with steady state heat flow?

A) 100°C
B) 93°C
C) 86°C
D) 80°C
E) 74°C