Is there a rule about consistency within a paragraph, of using past tense and past participle in alternate sentences? In my writing class, I notice some writers mix the two freely. Since I see this usage so often, I tend to see them as equivalent. Example:
"Jane sat down on the park bench. She had come to meet with her friend. She ate her lunch sandwich slowly, enjoying the sunshine. She had brought the sandwich in a brown paper bag. She carefully refolded the bag and put it in her pocket."