f(x)=(5x+3)(x-2)(3x+7)(x+5) has zeros at x=-5,x=-7/3,x=-3/5, and x=2 what is the sign of f on the interval -7/3

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )