$[9$ marks$]$ The cross$-$section of a heat exchanger for an oiling system is shown below. The hatching is cast aluminum and the oil flows in the area between the hatching. The oil flows through the $10-$foot long heat exchanger at $150$ gpm $.$ If the oil has a dynamic viscosity of $2\mathrm{.}25{10}^{-3}lb-\frac{s}{f}{t}^2$ and a specific gravity of $0\mathrm{.}91,$ determine the pressure drop in psi from one end of the heat exchanger to the other.