In question 1, shouldn’t the answer be 0? Because, say, you can think of the interval 0<w<9.
Regarding question 5, I don’t understand the use of “largest” in the question. For any value larger than 25, y will be positive; hence, p can go up to infinite and still satisfy the restriction of y being positive. Shouldn’t it be “what is the smallest value of p beyond which y is always positive”?