In a city of a fixed population of "P" people , the rate of change (with respect to time t) of the number "N" of people with a certain contagious disease is proportional to the product of the number...

Differential Equation

Extracted text: In a city of a fixed population of "P" people , the rate of change (with respect to time t) of the number "N" of people with a certain contagious disease is proportional to the product of the number who have disease and the number who do not. Which option is a differential equation which describes this situation? KN (P + N) dt = K N +(P dt – N)) dP dt KN(P - N) KN(P N) dt