The size distribution by mass of the dust carried in a gas, together with the efficiency of collection of each size range were reported as in the Table. The dust load is $30\frac{g}{m^3}$ where the gas flow rate is $500\frac{L}{s}.$ The sphericity of the particles is $0\mathrm{.}571$ with a density of $2500k\frac{g}{m^3}.0\mathrm{.}025\frac{S}{m}m$

a$-$ Fill in the missing values in the table $(40$ Marks$).$

less than $40$

b$-$ The volume$-$surface mean diameter of the dust particles in $mm(10$ Marks$).$

c$-$ Calculate the mass $($in $kg)$ of collected dust in one day $(20$ Marks$).$

d$-$ Surface area of this dust sample in Marks$).$