Find the constant of variation for the relation and use it to write an equation for the statement. then solve the equation. if y varies inversely as the square of x, and y=1/8 when x=1 find y when x=5

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! )