i$.$ Start from equation $1\mathrm{.}1$ to $1\mathrm{.}3,$ show that the pressure variation in the atmosphere is given as:

$P=P_s(1-\frac{a*z}{T_s}{)}^{\frac{g_s}{a_s*R}}$

Where $P_s=101325Pa,$ Ts $=(15+273)K,g_s=9\mathrm{.}81\frac{m}{s^2},$ subscript $s=$ sea$-$level.

ii$.$ An aircraft weighing $750$ kN when empty has a wing planform area $A_P$ of $150m^2.$ It cruises at an altitude of $9000$ m with a $10\mathrm{.}0$ angle of attack. Also, the wing characteristics of the airfoil are shown in the figure below. If its maximum allowable weight of the cargo is $550$ kN $,$ determine the following parameters:

$($i$).$ Determine the velocity of the aircraft.

$($ii$).$ Determine the Drag coefficient $C_{D,}$ if the wing span s is $30$ m $.$