ian tosses a bone up in the air for his dog, spot. the height, h, in feet, that spot is above the ground at the time t seconds after she jumps for the bone can be represented by the function, h(t) = -16t + 20t. What is spot's average rate of ascent, in feet per second, from the time she jumps into the air to the time she catches the bone at t = 1/2 second?