A three-person committee must be chosen from a group of 7 professors and 20 graduate students. If at least one of the people on the committee must be a professor, how many different groups of people could be chosen for the committee? Choose one:	A) A)70	B) B)1785	C) C)630	D) D)1,260	E) E)1,980
Total number of ways to select at least one professor = Number of ways to select 3 people from 20 students and 7 professors - Number of ways to select 3 people from 20 student (i.e. without including any professor)   = 27C3 - 20C3 = 2925 - 1140= 
<gadget id="calculator">2925 - 1140</gadget>
<output>1_785</output>
1785   ANSWER:1785
<result>B</result>
A three-person committee must be chosen from a group of 7 professors and 20 graduate students. If at least one of the people on the committee must be a professor, how many different groups of people could be chosen for the committee?