The revenue and cost functions, both in dollars, for the production and sale of x TVs are given as R(x) = 160x - 0.4x- and C(x) = 3,250 + 18x, respectively. (a) Find the value(s) of x where the graph of R(x) has a horizontal tangent line with correct units. (Enter your answers as a comma-separated list. Round your answers to the nearest integer. If an answer does not exist, enter DNE.) X = --Select-- (b) Find the profit function in terms of x. (Note: Profit is revenue minus costs.) P(X) = (c) Find the value(s) of x where the graph of P(x) has a horizontal tangent line with correct units. (Enter your answers as a comma-separated list. Round your answers to the nearest integer. If an answer does not exist, enter DNE.) X = -- Select-- Submit Answer MY NOTES