$15,0001\frac{b}{h}$ of benzene will be heated from $80F$ to $120F$ by cooling a stream of orthotoluidine $(C_7{H}_9(N))$ from $160F$ to $100F$ Inlet pressures are $40$ psia for ortho$-$toluidine and

$50$psia for benzene. A maximum pressure drop of $15$ psia is specified for each stream. A number of used carbon steel hairpins are available for this service. The hairpins are each $20ft$ long with $3-$in$.$ schedule $40$ outer pipe, $1\mathrm{.}5-$in$.$ un$-$finned schedule $40$ inner pipe, internal return bends and $2-$in$.$ schedule $40$ nozzles. Properties of ortho$-$toluidine at $130F$ are given below. Determine the number and configuration of hairpins required for this service.

$\backslash$table$[[$Property$,$Value$],[k(BT\frac{U}{h}ftF),0\mathrm{.}081],[(cP),{1\mathrm{.}85}^{**}$