Let f be the following piecewise-defined function. f(x) = x + 3 for x$4 4x + 3 for x > 4 (a) Is f continuous at x = 4? (b) Is f differentiable at x = 4? (a) Is f(x) continuous at x = 4? Yes O No (b) Is f(x) differentiable at x = 4? Yes O No