Which of the following statements are correct regarding the theory of consumer behavior?

1.  The indifference curve represents a set of consumption bundles that provide the consumer with the same level of satisfaction.
2. The marginal rate of substitution is the slope of the indifference curve.
3. The budget constraint determines the consumer's optimal choice by restricting the set of feasible consumption bundles.
4. The consumer always chooses the bundle that maximizes utility, regardless of the budget constraint.