A Bimetallic Beam of Aluminum $\left( E _ { a } = 70 \mathrm { GPa } \right) \text { and copper } \left( E _ { c } = 110 \mathrm { GPa } \right)$

A bimetallic beam of aluminum $\left( E _ { a } = 70 \mathrm { GPa } \right) \text { and copper } \left( E _ { c } = 110 \mathrm { GPa } \right)$ strips has a width of b = 25 mm; each strip has a thickness of t = 1.5 mm. A bending moment of 1.75 N . m is applied about The z axis. The ratio of the maximum stress in aluminum to that in copper is approximately:

A) 0.6
B) 0.8
C) 1.0
D) 1.5