P(at least 4 schools w/contract) is the same as 1 minus P( 0, 1, 2, 3 schools have contract)
2nd question I will leave alone for now, maybe after this post you will see how to solve
P(at most 4 schools w/contract) = P(0,1,2,3,4 schools have contract).
I will never give you keystrokes because 1) I dont own such calculators and couldnt tell you if I wanted to; and 2) I wouldn't tell you if I could, it would defeat the purpose for learning which I hope is the goal you seek (rather than the solution to to the problem per se)
I am happy to walk you through further if you want to learn rather than get answer to problem