Cagney can frost a cupcake every 20 seconds and Lacey can frost a cupcake every 30 seconds. Working together, how many cupcakes can they frost in 5 minutes?<spanclass=′latex−bold′>(A)</span>10<spanclass=′latex−bold′>(B)</span>15<spanclass=′latex−bold′>(C)</span>20<spanclass=′latex−bold′>(D)</span>25<spanclass=′latex−bold′>(E)</span>30