If xj ∈ {0, 1}, write a constraint to enforce the logical condition that x1 can be 1 only if both x2 = 1 and x3 = 1 (in other words, if either x2 = 0 or x3 = 0 then x1 = 0 but if both x2 = 1 and x3 = 1 then x1 can be either 0 or 1). is your constraint linear in the xj?