An organic solution is cooled from $121$ oC to $82$ oC at a flow rate of $1\mathrm{.}9$ tons$/$min$.$ Cooling water flows in the tubes with a flow rate of $3\mathrm{.}166$ tons$/$min at $27$ oC$.$ There are a total of $160$ tubes in the heat exchanger and the tubes are placed in a $1$ inch $14$ BWG $($di $=21\mathrm{.}2$ mm$,$ do $=25\mathrm{.}4$ mm$,$ xw $=2\mathrm{.}1$ mm$),$ p $=11/4$ inch square arrangement and the distance between obstacles is $31\mathrm{.}8$ mm$.$ The shell material is mild steel and the tube material is $304$ stainless steel. Cph$=$ Cpc$=4185$ J$/$kg oC and the shell inner diameter is $2\mathrm{.}42$ m$.$ Calculate tube lengths for:

$(1-2)$ type heat exchanger,

$(2-4)$ type heat exchanger.

Note: Take the physicochemical properties of the organic solution as the same as those of water and assume $/$w$\backslash$cong $1.$

Note: Please solve the question step by step and use colburn and donohue equation.