(5) The total electrical resistance is measured in ohms ($) in a circuit that has three individ- ual resistances represented by r, y, and z is given by the formula R(r, y, z) = cyZ yz+zxtry' Suppose at a given time the r resistance is 1000, the y resistance is 2000, and the z resistance is 30002. Also, suppose the r resistance is increasing at a rate of 20/min, the y resistance is increasing at the rate of 10/min, and the z resistance has no change. Find the rate of change of the total electrical resistance in this circuit at this time