Cb is the block co-efficient or co-efficient of fitness is the ratio of the volume of displacement to the product of length, breadth and draught

$$\because\space C_{b}\space=\space{{\nabla}\over L\times B\times D}\:---\:1$$

$$C_{p}\space=\space{{\nabla}\over L\times A_{m}}\:---\:2$$

$$C_m \space = \space {{A_m} \over B \times D}$$

$$A_{m}=\:C_{m}\times B\times D\:---\:3$$

Substitute 3 in 2

$$C_{p}\space=\space{{\nabla}\over C_{m}\times B\times D\ \times L}\:---\:4$$

$$\nabla=C_{b}\times L\times B\times D\:---5\:\left(from\:equation\:1\right)$$

Substitute 5 in 4

$$C_{p}=\frac{C_{b}\times L\times B\times D}{C_{m}\times L\times B\times D}$$

$$C_p \space = \space {{C_b} \over C_m}$$

$$Length \space of \space ship \space = \space L$$

$$Draught \space = \space {{L} \over 18 }$$

$$breadth \space = \space 2.1 \times draught \space = \space 2.1 \times {{L} \over 18}$$

$$TPC\:in\:SW\:=\:0.01025A_{w}$$

$$TPC\:in\:FW\:=\:0.0100A_{w}$$

$$0.01025A_{w}-0.0100A_{w}=0.7$$

$$A_{w}=\frac{0.7}{2.5\times10^{-4}}=2800$$

$$C_w \space = \space {{A_w} \over L \times B}$$$$0.83 \space = \space {{2800} \over L \times {{2.1L} \over 18}}$$

$$L=170.04m$$

$$TPC\:in\:FW=0.010\times A_{w}$$

$$=\:0.0100\times2800$$

$$TPC\:in\:FW=28$$