The differential equation below models the temperature of a 91°c cup of coffee in a 21°c room, where it is known that the coffee cools at a rate of 1°c per minute when its temperature is 71°c. solve the differential equation to find an expression for the temperature of the coffee at time t. (let y be the temperature of the cup of coffee in °c, and let t be the time in minutes, with t = 0 corresponding to the time when the temperature was 91°c.) dy/dt =(− 1/50)(y − 21)