Two bars are unstressed and have lengths of 25cm and 30cm at 20° as shown in Figure. Bar (1) is of aluminium and bar (2) is of steel. The cross-sectional area of bars are 20cm² for aluminium and 10cm² for steel. Assuming that the top and bottom supports are rigid, stress in Al and steel bars in $\frac{\mathrm{N}}{{\mathrm{mm}}^2}$ when the temperature is 70⁰C. (Nearly ) 

$\begin{array}{l}\left({\mathrm{Y}}_{\mathrm{a}}=0.70\times {10}^5\mathrm{N}/{\mathrm{mm}}^2\cdot {\mathrm{Y}}_{\mathrm{s}}=2.1\times {10}^5\mathrm{N}/{\mathrm{mm}}^2\right.\\ \left.{\mathrm{\alpha }}_{\mathrm{a}}=24\times {10}^{-6}{/}^{\circ }\mathrm{C}\text{ and }{\mathrm{\alpha }}_{\mathrm{s}}=12.\times {10}^{-6}{/}^{\circ }\mathrm{C}\right)\end{array}$

• A

  75, 150

• B

  25, 50

• C

  50, 100

• D

  100, 200