In a survey of investors it was found that 100 invested in stocks, 60 in mutual funds, and 50 in bonds. Of these, 35 invested in stocks and mutual funds, 30 in mutual funds and bonds, 28 in stocks and bonds, and 20 in all three. Determine the following while showing work.
a. The number of investors that participated in the survey.
b. How many invested in stocks or mutual funds but not in bonds?
c. How many invested in exactly one type of investment?