[{"price":0.50,"sale":true,"qty":12},{"price":0.99,"sale":true,"qty":4},{"price":1.99,"sale":true,"qty":12},{"price":2.50,"sale":true,"qty":12},{"price":1.99,"sale":true,"qty":22},{"price":1.98,"sale":false,"qty":1}]

db.collection.find({$and:[{$or:[{price:0.99},{price:1.99}]},{$or:[{sale:true},{qty:{$lt:20}}]}]})