Show that any integer n > 12 can be written as a sum 4r + 5s for some nonnegative integers r, s. (this problem is sometimes called a postage stamp problem. it says that any postage greater than 11 cents can be formed using 4 cent and 5 cent stamps.)

Many newspapers carry a certain puzzle in which the reader must unscramble letters to form words. how many ways can the letters of emdangl be arranged? identify the correct unscrambling, then determine the probability of getting that result by randomly selecting one arrangement of the given letters.