A mail-order firm, Amazing Co, can use one of 3 shipping couriers. Ajax Shipping charges $6 per pound and delivers in 2 days. Bilco Lanes charges $9 per pound but guarantees next-day delivery. The final courier, Hobo Ltd, charges only $3 per pound but takes 4 days to deliver. Amazing Co has a quarterly budget of $280,000 and a reputation for timely delivery. Formulate the linear program so that the firm delivers as fast as possible within budget for 70,000 pounds of shipments per quarter.

Let:
X1 = pounds using Ajax
X2 = pounds using Bilco
X3 = pounds using Hobo