Consider a room with a volume, V = 2100 {rm m}^3, containing machinery that produces carbon monoxide (CO) at a rate Q(t) = 0.0042 {rm m}^3/{rm hr}. Assume that ventillation brings fresh air into the room (assume constant volume and constant pressure) where it mixes completely, then exhausts at a rate of f = 8 {rm m}^3/{rm hr}. If c(t) is the concentration of CO in the room at any time, then the differential equation describing this situation is given by (use 'c' for the variable for concentratio