$($b$)$ The CIBSE Lighting Guide and British Standards recommend the following formula to calculate the average daylight factor for a side$-$lit room under a standard overcast sky with a lean glazing as follows:

$D{F}_{av}=\frac{T{A}_w}{A(1-R^2)}\%$

Please explain each of the parameters used in the formula. Which of these parameters are related to the amount of daylight available at the window?

$(5$ marks$)$

$($c$)$ Consider two small rooms in a same building, one on the ${40}^{th}$ floor and the other on the ground floor. This building is facing a group of other buildings with the same height in a row at a distance $30$ m apart $($see Figure Q$3).$ The window plane can be assumed to be at the outer wall surface of the building. Room dimensions: $,$ width $($along window wall$)=2\mathrm{.}5m$;

depth $($perpendicular to window wall$)=3m$;

floor to ceiling height $=3m$; floor to floor height $=3\mathrm{.}2m.$

Window in one wall only: window width $=2m$; window height $=1\mathrm{.}3m$;

Sill height $=1\mathrm{.}2m$; glazing transmittance $=0\mathrm{.}7$

Room surface reflectance: ceiling $=0\mathrm{.}8$; walls $=0\mathrm{.}5$; floor $=0\mathrm{.}2$; window $=0\mathrm{.}1$

Please calculate the average daylight factor for these two rooms.

$(10$ marks$)$

$($d$)$ In recent years, we use climate$-$based daylight modeling $($CBDM$)$ for characterizing the quality and quantity of daylight in a space. Please list and define the various metrics derived from CBDM$.$

$(5$ marks$)$

for c part need detailed solution for both rooms

fig is given and use b part equation