Answer the following questions about the sphere whose equation is given by x + y + x - 4x + 10y = - 1. Find the radius of the sphere. Radius: r = 71. 2. Find the center of the sphere. Write the center as a point (a, b, c) where a, b, and c are numbers. Center: (1 point) A car rental company charges a one-time application fee of 35 dollars, 60 dollars per day, and 15 cents per mile for its cars. (a) Write a formula for the cost, C, in dollars of renting a car as a function of the number of days, d, and the number of miles driven, m. C = (b) If C = f(d, m), then f(3, 680) =