1.The electrical resistance R of a wire varies inversely as the square of its diameter d. If a 25-foot wire with diameter 2 millimeters has a resistance 0.5ohm

(1) the constant of variation

(2) the variation model

(3) the rate when the diameter is 8 micrometers

2. A golf ball is hit so that it's height h in feet after t second is h(t) =-16t^2+70t

(1) what is the initial height of the golf ball?

(2) how high is the golf after 1.8 seconds?

(3) when will the ball reach its maximum height?

(4) The maximum height of the ball.