计算题：如图所示，某混联电路电压U=220V，已知R<sub>1</sub>=10<img src="/Image1/ef/ef2f9b7a3d056a0fe40378ac08e3ff83.jpg" />、R<sub>2</sub>=10<img src="/Image1/ef/ef2f9b7a3d056a0fe40378ac08e3ff83.jpg" />、R<sub>3</sub>=4<img src="/Image1/ef/ef2f9b7a3d056a0fe40378ac08e3ff83.jpg" />、R<sub>4</sub>=4<img src="/Image1/ef/ef2f9b7a3d056a0fe40378ac08e3ff83.jpg" />，求该电路的电流I。 <img src="/Image1/a8/a8cd090eed5a7f5d9a937a7885b6fae9.jpg" />