For the function, find the points on the graph at which the tangent line is horizontal. If none exist, state that fact.

$y=\frac{4}{3}{x}^3-7x2$

Select the correct choice below and, if necessary, fill in the answer box within your choice.

A$.$ The point$($s$)$ at which the tangent line is horizontal is $($are$).$

$($Type an ordered pair. Use a cormma to separate answers as needed. Type an exact answer, using radicals as needed.$)$

B$.$ There are no points on the graph where the tangent line is horizontal.

C$.$ The tangent line is horizontal at all points of the graph.