Answear: The differential equation, with proportionality constant k, is (M - T).
dT/dt = k(M - T)
Explanation:
where T is the temperature of the coffee at time t and M is the fixed temperature of the air at time t. The proportionality constant k represents the rate at which heat is transferred between the coffee and the air. This equation is a first-order linear ordinary differential equation, which means that its solution is a function T(t) that depends only on the initial conditions of the system.