3 points for completing every question; -1 if missing any question until whole 3 points are taken off. If missing questions listed below, this point won't get deduct.

hw_lect7_2: 2 points; .5 for showing lambda = 2.1; .5 for showing pr(x=0); .5 for process; .5 for final answer.

hw_lect8_3: 2 points;  1 point for each section; need to show process in order to get full point. 

1.55: 3 points; 1 point for each section; -0.5 if not showing process.