6. (2 pts) There are 10 points A,B,C,D,E,F,G,H,I,J in a given plane, no three on the same line. (a) How many lines are determined by these points? (1)) How many of these lines pass through point C? (c) How many triangles are determined by the points? 7. (3 pits) A student is to answer 10 out of 15 questions of an exam. (a) How many choices has he? (b) How many if he must answer the rst 5 questions? ((2) How many if he must answer 5 of the rst 8 questions? 3 (d How many if he must answer at least 5 of the rst 8 questions