A committee of four is selected from a total of 4 freshmen, 5 sophomores, and 6 juniors (obviously without replacement since one person can't simultaneously fill two committee spots).

Using combinations, determine the probability that:

a.at least three freshmen.are selected

Enter probability as a fraction or as a decimal rounded to nearest thousandth (three places).Examples of correctly entered responses:

3/55/110.3000.6500.971

________

b.all four selected are of the same class (order of selection doesn't matter)

Enter probability as a fraction or as a decimal rounded to nearest thousandth (three places).Examples of correctly entered responses:

3/55/110.3000.6500.971

________

c.all four selected are NOT of the same class (order of selection doesn't matter)

Enter probability as a fraction or as a decimal rounded to nearest thousandth (three places).Examples of correctly entered responses:

3/55/110.3000.6500.971

________

d.exactly three of the same class are selected (order of selection doesn't matter)

Enter probability as a fraction or as a decimal rounded to nearest thousandth (three places).Examples of correctly entered responses:

3/55/110.3000.6500.971