SHOW ALL YOUR WORK PLEASE step by step question $1,2,3,4$ attached below answer for all needed, btw:

Treat the concentrated phosphoric acid $(95\%$ PA$,5\%$ water$)$ as pure phosphoric acid.

Cooling water is available at $180$C and has a maximum return temperature of $400$C$,$ the mixer outlet stream is $3\mathrm{.}41/$gc if it wasnt clear