question: How does the performance of linear receiver processing compare to non-linear receiver processing in terms of SE (Spectral Efficiency)? option 1: Linear processing achieves higher SE than non-linear processing option 2: Linear processing achieves the same SE as non-linear processing option 3: Linear processing achieves lower SE than non-linear processing option 4: The performance loss of linear processing depends on the number of UEs option 5: Linear processing is only optimal when there is no interference 