Solve problem in picture please Part $1$: Forced Convection Heat Transfer Through a Tube Bank

A plan to use a steam powered preheater to raise the incoming fresh air to a deck air handler from a planed $\backslash (0^\{\backslash$circ$\}\backslash$mathrm$\{$C$\}\backslash )$ to $\backslash (25^\{\backslash$circ$\}\backslash$mathrm$\{$C$\}\backslash ).$ The air duct has a width $250$ mm with the tube spacings of $\backslash (\backslash$mathrm$\{$S$\}\_\{\backslash$mathrm$\{$L$\}\}=\backslash$mathrm$\{$S$\}\_\{\backslash$mathrm$\{$T$\}\}=24\backslash$mathrm$\{$~mm$\}\backslash ).$ The tubes of a prebuilt assembly can be as many as $4$ tubes in the transverse direction and $3$ tubes in the longitudinal direction. The air velocity is measured at $\backslash (12\backslash$mathrm$\{$~m$\}/\backslash$mathrm$\{$s$\}\backslash )$ at the inlet of the tune assembly. The tube surface is held at $\backslash (125^\{\backslash$circ$\}\backslash$mathrm$\{$C$\}\backslash ).$ How many of the units are needed in series to reach the goal of reheating to a temperature higher than $\backslash (25^\{\backslash$circ$\}\backslash$mathrm$\{$C$\}\backslash )?$

Problems

A$)$ Determine the total rate of heat transfer to the air and the temperature of the air leaving the duct heater of one set of heating elements.

B$)$ How many sets of heating elements would be needed to just meet the design goal? What would the temperature be after the unit$($s$),$ if not regulated to $\backslash (25^\{\backslash$circ$\}\backslash$mathrm$\{$F$\}\backslash ).$

C$)$ What would the pressure drop be after the unit$($s$)?$