Thus the revenue is increasing at the rate of $_____ per day i dont know how to sub in the answers to get the correct answer! 2. Originally Posted by samtheman17 The rate of change of q with respect to time (in days) is dq/dt= 60 . The rate of change of revenue over time, dR/dt, is to be found when q= 480 . Differentiate both sides of the equation R= 120 q- q^2/240 with respect to t to get dR/dt= 120 dq/dt − 1/ 120 q dq/dt. Now substitute the known values for q and dq/dt to get dR/dt= ___*___ - 1/ ___ * ___ * ___ Thus the revenue is increasing at the rate of$_____ per day