Determine whether the lines l1 and l2 are parallel, skew, or intersecting. l1: x = 9 + 6t, y = 12 − 3t, z = 3 + 9t l2: x = 4 + 16s, y = 12 − 8s, z = 16 + 20s

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! )