$650g$ of a certain substance is heated at constant pressure from $70C$ to $90C.$ Specific heat capacity at constant pressure is given by the following expression:

$4C{p}^2-7Cp=5$

Where:

$Cp=$ specific heat capacity at constant pressure in $k\frac{J}{k}g-K.$

Determine the change in entropy in $\frac{J}{K}.$