A box with mass m is dragged across a level floor with coefficient of kinetic friction μk by a rope that is pulled upward at an angle θ above the horizontal with a force of magnitude F. (a) In terms of m, μk, θ, and g , obtain an expression for the magnitude of the force required to move the box with constant speed. (b) Knowing that you are studying physics, a CPR instructor asks you how much force it would take to slide a 90-kg patient across a floor at constant speed by pulling on him at an angle of 25∘ above the horizontal. By dragging weights wrapped in an old pair of pants down the hall with a spring balance, you find that μk=0.35. Use the result of part (a) to answer the instructor’s question.