A company uses 4 pounds of resource 1 to make each unit of X1 and 3 pounds of resource 1 to make each unit of X2. There are only 150 pounds of resource 1 available. Which of the following constraints reflects the relationship between X1, X2 and resource 1?
a. 4 X1 + 3 X2 ≥ 150
b. 4 X1 + 3 X2 ≤ 150
c. 4 X1 + 3 X2 = 150
d. 4 X1 ≤ 150