A bullet is fired upward from ground level. Its height above the ground (in feet) at time t seconds is given by the following equation. H(t) = -1612+ 640t (a) Find the vertex. (b) Find the time at which the bullet reaches its maximum height. (c) Find the maximum height. (d) Find the time at which the bullet hits the ground (when the height is equal to zero). (a) What equation can be used to calculate the t-coordinate of the vertex? 640 O A t= 2(-16) O B. 1 2(-16) 640 640 OC. t= 2(-16) OD. 1= _ 2(-16) 640 The vertex is at (Type an ordered pair, Do not use commas in the individual coordinates.) (b) The bullet reaches at maximum at seconds. (Type a whole number.) (c) The maximum height of the bullet is feet. (Type a whole number.) (d) The bullet hits the ground at seconds