18. JBC Corporation is owned 20 percent by John, 30 percent by Brian, 30 percent by Charlie, and 20 percent by Z Corporation. Z Corporation is owned 80 percent by John and 20 percent by an unrelated party. Brian and Charlie are brothers. Answer each of the following questions about JBC under the constructive ownership rules of Section 267: a. What is John's percentage ownership? b. What is Brian's percentage ownership