A $12-$meter simply supported beam carrying a uniform dead load of $6$ kN$/$m including its own weight, and a service live load of $9$ kN$/$m in addition to a concentrated dead load of $22$ kN at midspan. Given fc$=27\mathrm{.}6$ MPa, and fy $=414$ MPa, calculate the instantaneous midspan deflection of the beam. Use modular ratio of $8.$

Beam details: b $=325$ mm$,$ h $=625$ mm$,$ d $=525$ mm$,$ reinforced with $2$ layers of $25-$mm diameter tension bars $($only$),$ with each layer having $4$ bars. Answer: $48\mathrm{.}182$ mm