Ms. Harshey rewards students with a piece of chocolate (approximately 60 calories) for every day that they had in an assignment. David handed in 7/8 of Ms. Hershey’s assignment over the past school year. Given that 30 minuets of play burn 150 calories, how many assignment did Ms. Harshey assign if it took David 28 hours to burn off all the calories from the chocolate he earned?