The figure shows a steel piece of diameter 20 mm at A and C, and 10 mm at B. The lengths of three sections A, B and C are each equal to 20 mm. The piece is held between two rigid surfaces X and Y. The coefficient of linear expansion $\alpha = 1.2\times 10^{-5}/_{}^{0}\textrm{C}$ and Young’s modulus $E = 2\times 10^{5}MPa$ for steel
When the temperature of this piece increases by $50_{}^{0}\textrm{C}$ the stresses in sections A and B are
(a) 120 MPa and 480 MPa
(b) 60 MPa and 240 MPa
(c) 120 MPa and 120 MPa
(d) 60 MPa and 120 MPa