Expected production hours $($in a given month$)$ for a family of products $($Hard gelatin capsules$)$ are $637$ hours. If the worker works for $9\frac{h}{?}$ day and there are $6$ leaves in a month of $31$ days, how many workers are required to complete the production?

a$.,3\mathrm{.}79$

b$.2\mathrm{.}83$

C$.2\mathrm{.}28$

d$.1\mathrm{.}91$