Explanation

B:

given: A1 = 1.2×10$^3$ cm$^2$ , 40 = 40 - 0 °C = 40 °C

using $\beta$ = 2$\alpha$ = $\frac { A _2  - A _1}{A_1 \delta\theta}$ $_1$

A$_2$ - A$_1$ =$\delta$ A = 2$\alpha$ A$_1$ $\delta$ $\theta$

= 2x1.2×10$^{-}{5}$ x1.2×103×40

$\delta$ A=115.2×10$^{-}{2}$

= 1.15 cm$^2$

B:

given: A1 = 1.2×10$^3$ cm$^2$ , 40 = 40 - 0 °C = 40 °C

using $\beta$ = 2$\alpha$ = $\frac { A _2  - A _1}{A_1 \delta\theta}$ $_1$

A$_2$ - A$_1$ =$\delta$ A = 2$\alpha$ A$_1$ $\delta$ $\theta$

= 2x1.2×10$^{-}{5}$ x1.2×103×40

$\delta$ A=115.2×10$^{-}{2}$

= 1.15 cm$^2$