Can you explain how to solve this math problem: There were 90 people at the summer picnic.  There were 50 soda cans, 50 plastic bottles of sparkling water, and 50 glass bottles of juice.  One-half of the guests drank soda, one-third of the guests drank sparkling water, and four-fifths of the juices were consumed.  How many recyclable cans and bottles were collected?