The force F on an object is the product of the mass m and the acceleration a. In this problem,
assume that the mass and acceleration both depend on time t, hence so the does the force. That is,
F(t) = m(t)a(t)
At time t = 10 seconds, the mass of an object is 59 grams and changing at a rate of 7 g/s. At this same time, the acceleration is 8 m/s^2 and changing at a rate of -8 m/s^3
By the product rule, the force on the object is changing at the rate of