1. The electrical charge on a new cell phone decreases according to the function C(t)=-0.1t- -0.5t +15, where t is the time in hours following a full charge and C(t ) is a measure of the charge, in charge units. What is average rate at which the electrical charge decreases from t =0 to t =4 ? . What is the (instantaneous) rate at which the electrical charge decreases when t = 4? C. How long does one have until the charge is fully depleted? Hint: C(t)=0 when the charge is fully depleted. 2. Find the derivative of the function f by using rules of differentiation. a. f(x)=x -5x2 +12x-3 (Problem 2 continued) b. f (x ) =1 10,5 + 350/x +205X3+124