It's b. Group all the pounds together and all the volumes together. Small packages weigh 30 lbs (30x), lg pkgs weight 65 lbs (65y) and together they weigh at most 3800 lbs. So 30x + 65y <= 3800 (they divided each of those terms by 5 to get 6x + 13y <= 760). Next take the volumes: small pkgs have a volume of 4 ft^3 (4x) and lg pkgs have a volume of 9 ft^3 (9y) and together they are no more than 400 ft^3. So 4x + 9y <= 400. It's b.
