Employees of a certain unit plant trees in the suburbs. Among them, there are male employees and female employees, and (1/3) employees each bring a child to participate. Male employees planted 13 trees each, female employees planted 10 trees each, and each child planted 6 trees. They planted a total of 216 trees. How many of them are female employees?
某单位职工到郊外植树，其中有男职工，也有女职工，并有(1/3)的职工各带一个孩子参加．男职工每人种树13棵，女职工每人种树10棵，每个孩子种6棵，他们共种树216棵，那么其中女职工有多少人？
<result>3</result>