exam 3	exams 1+2+3
	percentile	score	total score
	100%	15	40
	90%	13.7	34.7
	80%	12	32
	70%	10	29.1
	60%	9.8	27
	50%	9	26
	40%	9	24
	30%	7.9	22.9
	20%	6.6	19.6
	10%	5	18.3
	0%	3	13