As finals are time consuming for students and professors, Professor Schlock has decided that students will draw cards to determine their grade. Each student will draw from a group of 6 cards placed face down on a table. One of the cards is black, and the others are red. The student will draw cards one at a time, and may stop at any point. For each red card drawn, the grade will be higher: one red card brings a D, two a C, three a B, and four an A. But, if the black card is drawn at any time, the student's grade will be an F. Draw the decision tree for this situation, assuming that grades my justifiably be quantified in the usual manner ( A=4, B=3, C=2 etc.)