Write informal negations of each statement. a. "Some dogs are unfriendly." b. "All cats love dogs." c. "All mice fear cats." d. "There is a mouse that loves a cat." Consider the following statements. Let D be "V real-valued functions f, if f is differentiable, then f is continuous." Let C be "3 a real-valued function f which is not continuous at x = a, yet its limit exists at x = a." a. Write the formal negation of D. b. Write the formal negation of C.