$1.$ If the maximum steel ratio for a singly reinforced condition is based on a maximum strain of $0\mathrm{.}004$ in the extreme tension reinforcement, and if f$$c$=35$ MPa, fy $=415$ MPa, fyh $=275$ MPa, concrete cover up the centroid of the reinforcement is $100$ mm$,$ which of the following most nearly gives dept of the compression stress block in term of its percentage to its effective depth.

a$.0\mathrm{.}8700$d

b$.0\mathrm{.}5147$d

c$.0\mathrm{.}3559$d

d$.0\mathrm{.}3429$d