Solve the Problem $t$ Seconds Is $h = - 10 t ^ { 2 } + 320 t$

Multiple Choice

Solve the problem.
-A projectile is thrown upward so that its distance above the ground after $t$ seconds is $h = - 10 t ^ { 2 } + 320 t$ After how many seconds does it reach its maximum height?

A) $32 \mathrm {~s}$
B) $16 \mathrm {~s}$
C) $8 \mathrm {~s}$
D) $24 \mathrm {~s}$