A$)$ A post$-$tensioned concrete beam of rectangular section. $100mm$ wide and $300mm$ deep, is stressed by a parabolic cable with zero eccentricity at the supports and an eccentricity of $50mm$ at the centre of span. The area of the cable is $200m{m}^2$ and initial stress in the cable is $1200\frac{N}{m}{m}^2.$ If the ultimate creep strain is $3010m\frac{m}{m}m$ per N$/$mm modulus of elasticity of steel is $210m{m}^2,$ compute the loss of stress in steel only due to creep of concrete.