Each week, Christian earns $x fixing bicycles and receives $10 as his allowance. To find how much he will earn in total over 2 weeks, Christian calculates: x + 10 + x + 10. What is another way Christian can calculate how much he will earn in total over the 2 weeks?
A.x + 10
B.2x + 10
C.x + 20
D.2(x + 10)