A mason is contracted to build a patio retaining wall. Plans call for the base of the wall to be a row of fifty 10-inch bricks, each separated by 1/2 -inch-thick mortar. Suppose that the bricks used are randomly chosen from a population of bricks whose mean length is 10 inches and whose standard deviation is 1/32 inch. Also, suppose that the mason, on the average, will make the mortar 1/2 inch thick, but that the actual dimension will vary from brick to brick, the standard deviation of the thicknesses being 1/16 inch. What is the standard deviation of L, the length of the first row of the wall? What assumption are you making?